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1.
Anal Bioanal Chem ; 412(1): 159-169, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31776642

RESUMO

Attenuated total reflectance-infrared (ATR-IR) spectroscopy is a robust tool for molecular characterisation of matter. Applied to semi-solid formulations, it enables rapid and reliable data collection without pre-analytical requirements. Based on nano-encapsulated Omegalight®, a skin-lightening active cosmetic ingredient (ACI), incorporated in a hydrogel, it is first demonstrated that, despite the high water content and the chemical complexity of the samples (i.e. number of ingredients), the spectral features of the ACI can be detected and monitored. Secondly, with a total of 105 samples divided into a training set (n = 60) and an unknown set (n = 45) covering a 0.5% w/w-5% w/w concentration range, the study further investigates the quantitative performance of ATR-IR coupled with partial least squares regression (PLSR). Through a step-by-step approach in testing different cross-validation protocols, accuracy (root mean square error of cross-validation (RMSECV)) and linearity between the experimental and predicted concentrations (R2) of ATR-IR are consistently evaluated to be respectively 0.097% (w/w) and 0.995 with a lower LOD = 0.067% (w/w). Subsequently, further evaluation of the accuracy (relative error of the predicted concentration compared with the true value, expressed as %) of the analysis was undertaken with the 45 unknown samples that were defined as unknown and analysed by PLSR. The outcome of the analysis demonstrates the ruggedness and the consistency of the determination performed using the ATR-IR data. With an average relative error of 2.5% w/w and only 5 samples out of 45 blind samples exhibiting a relative error above the 5% threshold, high accuracy quantification of the nano-encapsulated ACI can be unambiguously achieved by means of the label-free and non-destructive technique of ATR-IR spectroscopy. Ultimately, the study demonstrates that the analytical capabilities of ATR-IR hold significant potential for applications in the cosmetics industry, and although the path remains long, the present study is one step further to support validation of the technique, albeit for the specific case of Omegalight®.


Assuntos
Cosméticos/química , Espectrofotometria Infravermelho/métodos , Calibragem , Reprodutibilidade dos Testes
2.
J Agric Food Chem ; 68(1): 390-401, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31820962

RESUMO

Infrared spectroscopy is often used as a simple, fast, and green method to screen for economically motivated adulteration in spices. However, conventional microscopy remains the reference method. In this research, the combination of microscopy and Fourier-transform infrared spectroscopy in mapping mode, namely, micro-FTIR imaging, along with Principle Component Analysis were used to develop a non-targeted method for detecting a broad range of organic and mineral bulking agents that could potentially be used to adulterate black pepper. This method, based on the spatial distribution of black pepper chemical composition, has been thoroughly validated as a one-class, non-targeted classification method. Results are categorized as Typical or Atypical, where an Atypical result indicates a high probability of adulteration. For an Atypical outcome, a multitool investigational approach is then used for the detection and identification of the potential adulterant.


Assuntos
Contaminação de Alimentos/análise , Piper nigrum/química , Espectrofotometria Infravermelho/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Análise de Componente Principal , Sementes/química , Especiarias/análise
3.
Anal Bioanal Chem ; 412(3): 533-537, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31853603

RESUMO

Glycosaminoglycans (GAGs) are a physio- and pharmacologically highly relevant class of complex saccharides, possessing a linear sequence and strongly acidic character. Their repetitive linear core makes them seem structurally simple at first glance, yet differences in sulfation and epimerization lead to an enormous structural diversity with only a few GAGs having been successfully characterized to date. Recent infrared action spectroscopic experiments on sulfated mono- and disaccharide ions show great promise. Here, we assess the potential of two types of gas-phase action spectroscopy approaches in the range from 1000 to 1800 cm-1 for the structural analysis of complex GAG oligosaccharides. Synthetic tetra- and pentasaccharides were chosen as model compounds for this benchmark study. Utilizing infrared multiple photon dissociation action spectroscopy at room temperature, diagnostic bands are largely unresolved. In contrast, cryogenic infrared action spectroscopy of ions trapped in helium nanodroplets yields resolved infrared spectra with diagnostic features for monosaccharide composition and sulfation pattern. The analysis of GAGs could therefore significantly benefit from expanding the conventional MS-based toolkit with gas-phase cryogenic IR spectroscopy. Graphical abstract.


Assuntos
Glicosaminoglicanos/química , Oligossacarídeos/química , Espectrofotometria Infravermelho/métodos , Animais , Temperatura Baixa , Hélio/química , Humanos , Íons/química , Isomerismo , Espectrofotometria Infravermelho/instrumentação , Sulfatos/análise
4.
Bioelectrochemistry ; 132: 107443, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31869700

RESUMO

Planar asymmetric lipid bilayers composed of phosphatidylethanolamine and phosphatidylglycerol lipids are transferred onto a gold electrode surface. Lipids containing two saturated, one monounsaturated and two monounsaturated hydrocarbon chains compose the model membranes. Results of electrochemically controlled polarization modulation infrared reflection absorption spectroscopy and quartz crystal microbalance with energy dissipation studies reveal two different types of electric potential-dependent structural rearrangements in the bilayers. They are correlated with the geometry of the lipid molecule. Packing parameter correlates the cross-section area of the hydrophobic and hydrophilic parts of amphiphilic molecules. In bilayers composed of lipids with the packing parameter <1, the hydrocarbon chains are tilted with respect to the bilayer plane and the polar head groups are well hydrated. At a threshold potential an abrupt flow of water through the bilayer is connected with membrane dehydration and upward orientation of the chains. In bilayers composed of lipids with packing parameter ≥1, electric potentials have negligible effect on the membrane structure. A simple rule correlating the packing parameter with molecular scale changes occurring at electrified membranes has a large diagnostic implication for biomimetic studies and our understanding of molecular processes occurring in biological cell membranes.


Assuntos
Eletrodos , Lipídeos/química , Membranas Artificiais , Interações Hidrofóbicas e Hidrofílicas , Bicamadas Lipídicas/química , Espectrofotometria Infravermelho/métodos
5.
J Phys Chem Lett ; 10(24): 7878-7883, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31794222

RESUMO

Local probes are indispensable to study protein structure and dynamics with site-specificity. The isonitrile functional group is a highly sensitive and H-bonding interaction-specific probe. Isonitriles exhibit large spectral shifts and transition dipole moment changes upon H-bonding while being weakly affected by solvent polarity. These unique properties allow a clear separation of distinct subpopulations of interacting species and an elucidation of their ultrafast dynamics with two-dimensional infrared (2D-IR) spectroscopy. Here, we apply 2D-IR to quantify the picosecond chemical exchange dynamics of solute-solvent complexes forming between isonitrile-derivatized alanine and fluorinated ethanol, where the degree of fluorination controls their H-bond-donating ability. We show that the molecules undergo faster exchange in the presence of more acidic H-bond donors, indicating that the exchange process is primarily dependent on the nature of solvent-solvent interactions. We foresee isonitrile as a highly promising probe for studying of H-bonds dynamics in the active site of enzymes.


Assuntos
Alanina/química , Técnicas Biossensoriais/métodos , Espectrofotometria Infravermelho/métodos , Simulação por Computador , Ligação de Hidrogênio , Cinética , Modelos Moleculares , Conformação Molecular , Transição de Fase , Solventes/química , Vibração
6.
J Phys Chem Lett ; 10(24): 7672-7677, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31763851

RESUMO

Current submillisecond time-resolved broad-band infrared spectroscopy, one of the most frequently used techniques for studying structure-function relationships in life sciences, is typically limited to fast-cycling reactions that can be repeated thousands of times with high frequency. Notably, a majority of chemical and biological processes do not comply with this requirement. For example, the activation of vertebrate rhodopsin, a prototype of many protein receptors in biological organisms that mediate basic functions of life, including vision, smell, and taste, is irreversible. Here we present a dispersive single-shot Féry spectrometer setup that extends such spectroscopy to irreversible and slow-cycling systems by exploiting the unique properties of brilliant synchrotron infrared light combined with an advanced focal plane detector array embedded in a dispersive optical concept. We demonstrate our single-shot method on microbial actinorhodopsin with a slow photocycle and on vertebrate rhodopsin with irreversible activation.


Assuntos
Rodopsina/química , Imagem Individual de Molécula/instrumentação , Imagem Individual de Molécula/métodos , Espectrofotometria Infravermelho/instrumentação , Espectrofotometria Infravermelho/métodos , Cinética , Luz , Processos Fotoquímicos , Conformação Proteica
7.
Malar J ; 18(1): 341, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31590669

RESUMO

BACKGROUND: Epidemiological surveys of malaria currently rely on microscopy, polymerase chain reaction assays (PCR) or rapid diagnostic test kits for Plasmodium infections (RDTs). This study investigated whether mid-infrared (MIR) spectroscopy coupled with supervised machine learning could constitute an alternative method for rapid malaria screening, directly from dried human blood spots. METHODS: Filter papers containing dried blood spots (DBS) were obtained from a cross-sectional malaria survey in 12 wards in southeastern Tanzania in 2018/19. The DBS were scanned using attenuated total reflection-Fourier Transform Infrared (ATR-FTIR) spectrometer to obtain high-resolution MIR spectra in the range 4000 cm-1 to 500 cm-1. The spectra were cleaned to compensate for atmospheric water vapour and CO2 interference bands and used to train different classification algorithms to distinguish between malaria-positive and malaria-negative DBS papers based on PCR test results as reference. The analysis considered 296 individuals, including 123 PCR-confirmed malaria positives and 173 negatives. Model training was done using 80% of the dataset, after which the best-fitting model was optimized by bootstrapping of 80/20 train/test-stratified splits. The trained models were evaluated by predicting Plasmodium falciparum positivity in the 20% validation set of DBS. RESULTS: Logistic regression was the best-performing model. Considering PCR as reference, the models attained overall accuracies of 92% for predicting P. falciparum infections (specificity = 91.7%; sensitivity = 92.8%) and 85% for predicting mixed infections of P. falciparum and Plasmodium ovale (specificity = 85%, sensitivity = 85%) in the field-collected specimen. CONCLUSION: These results demonstrate that mid-infrared spectroscopy coupled with supervised machine learning (MIR-ML) could be used to screen for malaria parasites in human DBS. The approach could have potential for rapid and high-throughput screening of Plasmodium in both non-clinical settings (e.g., field surveys) and clinical settings (diagnosis to aid case management). However, before the approach can be used, we need additional field validation in other study sites with different parasite populations, and in-depth evaluation of the biological basis of the MIR signals. Improving the classification algorithms, and model training on larger datasets could also improve specificity and sensitivity. The MIR-ML spectroscopy system is physically robust, low-cost, and requires minimum maintenance.


Assuntos
Teste em Amostras de Sangue Seco/instrumentação , Malária Falciparum/diagnóstico , Plasmodium falciparum/isolamento & purificação , Espectrofotometria Infravermelho/métodos , Aprendizado de Máquina Supervisionado , Humanos , Modelos Logísticos , Malária Falciparum/sangue , Tanzânia
8.
Malar J ; 18(1): 348, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31619246

RESUMO

BACKGROUND: Widespread elimination of malaria requires an ultra-sensitive detection method that can detect low parasitaemia levels seen in asymptomatic carriers who act as reservoirs for further transmission of the disease, but is inexpensive and easy to deploy in the field in low income settings. It was hypothesized that a new method of malaria detection based on infrared spectroscopy, shown in the laboratory to have similar sensitivity to PCR based detection, could prove effective in detecting malaria in a field setting using cheap portable units with data management systems allowing them to be used by users inexpert in spectroscopy. This study was designed to determine whether the methodology developed in the laboratory could be translated to the field to diagnose the presence of Plasmodium in the blood of patients presenting at hospital with symptoms of malaria, as a precursor to trials testing the sensitivity of to detect asymptomatic carriers. METHODS: The field study tested 318 patients presenting with suspected malaria at four regional clinics in Thailand. Two portable infrared spectrometers were employed, operated from a laptop computer or a mobile telephone with in-built software that guided the user through the simple measurement steps. Diagnostic modelling and validation testing using linear and machine learning approaches was performed against the gold standard qPCR. Sample spectra from 318 patients were used for building calibration models (112 positive and 110 negative samples according to PCR testing) and independent validation testing (39 positive and 57 negatives samples by PCR). RESULTS: The machine learning classification (support vector machines; SVM) performed with 92% sensitivity (3 false negatives) and 97% specificity (2 false positives). The Area Under the Receiver Operation Curve (AUROC) for the SVM classification was 0.98. These results may be better than as stated as one of the spectroscopy false positives was infected by a Plasmodium species other than Plasmodium falciparum or Plasmodium vivax, not detected by the PCR primers employed. CONCLUSIONS: In conclusion, it was demonstrated that ATR-FTIR spectroscopy could be used as an efficient and reliable malaria diagnostic tool and has the potential to be developed for use at point of care under tropical field conditions with spectra able to be analysed via a Cloud-based system, and the diagnostic results returned to the user's mobile telephone or computer. The combination of accessibility to mass screening, high sensitivity and selectivity, low logistics requirements and portability, makes this new approach a potentially outstanding tool in the context of malaria elimination programmes. The next step in the experimental programme now underway is to reduce the sample requirements to fingerprick volumes.


Assuntos
Computação em Nuvem , Testes Diagnósticos de Rotina/métodos , Gerenciamento Clínico , Malária/diagnóstico , Espectrofotometria Infravermelho/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Tailândia , Adulto Jovem
9.
Analyst ; 144(21): 6334-6341, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31553337

RESUMO

Antibody aggregates may occur as undesirable by-products during the manufacturing process of biopharmaceutical proteins since parameters such as pH, temperature, ionic strength, protein concentration, oxygen, and shear forces can lead to aggregate formation. These aggregates have to be detected, quantified and removed cost extensively, since they may reduce the safety and efficacy of the product. Protein aggregates can range from small soluble dimers up to large visible agglomerates. Differently aggregated antibody samples were characterized for their soluble and insoluble aggregate concentration by size exclusion chromatography and fluorescence microscopy, respectively. The samples exhibited a high diversity of protein aggregates, which varied in amount, size and shape. For secondary structure characterization, infrared attenuated total reflection (IR-ATR) and two-dimensional fluorescence (2D-FL) spectroscopy were applied. Using direct spectroscopy, only marginal differences of various antibody aggregates were evident. However, using appropriate chemometric strategies, the evaluation of IR-ATR and 2D-FL spectra yielded the discrimination of differently aggregated antibody samples with yet unprecedented precision.


Assuntos
Anticorpos Monoclonais/análise , Agregados Proteicos , Animais , Anticorpos Monoclonais/química , Células CHO , Cricetulus , Imunoglobulina G/análise , Imunoglobulina G/química , Análise de Componente Principal , Estrutura Secundária de Proteína , Espectrometria de Fluorescência/métodos , Espectrofotometria Infravermelho/métodos
10.
Nucleic Acids Res ; 47(18): e108, 2019 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-31562528

RESUMO

The integrity of the chromatin structure is essential to every process occurring within eukaryotic nuclei. However, there are no reliable tools to decipher the molecular composition of metaphase chromosomes. Here, we have applied infrared nanospectroscopy (AFM-IR) to demonstrate molecular difference between eu- and heterochromatin and generate infrared maps of single metaphase chromosomes revealing detailed information on their molecular composition, with nanometric lateral spatial resolution. AFM-IR coupled with principal component analysis has confirmed that chromosome areas containing euchromatin and heterochromatin are distinguishable based on differences in the degree of methylation. AFM-IR distribution of eu- and heterochromatin was compared to standard fluorescent staining. We demonstrate the ability of our methodology to locate spatially the presence of anticancer drug sites in metaphase chromosomes and cellular nuclei. We show that the anticancer 'rule breaker' platinum compound [Pt[N(p-HC6F4)CH2]2py2] preferentially binds to heterochromatin, forming localized discrete foci due to condensation of DNA interacting with the drug. Given the importance of DNA methylation in the development of nearly all types of cancer, there is potential for infrared nanospectroscopy to be used to detect gene expression/suppression sites in the whole genome and to become an early screening tool for malignancy.


Assuntos
Cromossomos/ultraestrutura , DNA/ultraestrutura , Metáfase/genética , Espectrofotometria Infravermelho/métodos , Animais , Núcleo Celular/ultraestrutura , Eucromatina/ultraestrutura , Heterocromatina/ultraestrutura , Humanos , Interfase/genética
11.
Molecules ; 24(17)2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31484400

RESUMO

We report a varying temperature infrared spectroscopic (VTIR) study with partial deuterium isotopic exchange as a method for characterizing proton mobility in acidic materials. This VTIR technique permits the estimation of activation energies for proton diffusion. Different acidic materials comprising classical proton-conducting materials, such as transition metal phosphates and sulfonated solids, as well as different zeolites, are tested with this new method. The applicability of the method is thus extended to a vast library of materials. Its underlying principles and assumptions are clearly presented herein. Depending on the temperature ranges, different activation energies for proton transfer are observed irrespective of the different materials. In addition to the well-studied transition metal phosphates, Si-rich zeolites appear to be promising proton-transfer materials (with Eact < 40 kJ mol-1) for application in high-temperature (>150 °C) PEM fuel cells. They significantly outperform Nafion and sulfonated silica, which exhibit higher activation energies with Eact ~ 50 and 120 kJ mol-1, respectively.


Assuntos
Espectrofotometria Infravermelho/métodos , Zeolitas/química , Adsorção , Prótons , Temperatura
12.
J Food Sci ; 84(10): 2777-2784, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31524956

RESUMO

The aim of this work was to study the potential of using infrared spectroscopy and chemometrics to monitor Maillard reaction. Sodium caseinate (NaCAS) and gum Arabic (GA) or sodium carboxymethyl cellulose (CMC) powders were mixed at 1:1, spray-dried, and incubated at 60 °C and 76% of relative humidity from 0 to 72 hr. Sample infrared spectra were collected, and browning degree, conjugation efficiency, and stabilization properties of the conjugates were analyzed by spectrophotometry, fluorescence spectroscopy, turbidity, and zeta potential measurements. Pairwise soft independent modeling of class analogy (SIMCA) models showed significant chemical differences among NaCAS-GA mixtures incubated for 0 (Control) and 16 hr, attributed to functional groups linked to different Maillard reaction products such as Schiff's base and pyridine compounds. Infrared spectroscopy combined with SIMCA is a powerful tool to monitor the formation of protein-polysaccharide conjugates by Maillard reaction. PRACTICAL APPLICATION: Protein-polysaccharide conjugates obtained by Maillard reaction are currently used as novel food emulsifiers. However, conventional methods to study this chemical reaction are time consuming or involve the use of toxic and harmful reactants. Infrared spectroscopy combined with multivariate analysis is evaluated to be used as a rapid tool to monitor Maillard reaction.


Assuntos
Goma Arábica/química , Reação de Maillard , Espectrofotometria Infravermelho/métodos , Emulsificantes/química , Análise de Fourier , Análise Multivariada , Polissacarídeos/química , Proteínas/química
13.
Talanta ; 205: 120115, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450462

RESUMO

A set of 42 millet (panicum miliaceum L.) samples was investigated for its protein content using standard Kjeldahl analysis and near-infrared spectroscopy. The performance of three handheld spectrometers was compared to a benchtop instrument. The used spectrometers operate in different regions of the NIR, which gives interesting insights into the applicability of each region. Additionally, semi-automated, consumer-oriented multivariate data analysis was compared to sophisticated data evaluation. The performance of the near-infrared instruments was compared using important statistical parameters of the established cross- and test set validated partial least squares regression (PLS-R) models. Milled and intact samples were analysed, in order to further evaluate the importance of homogeneity. The results showed that the benchtop spectrometer is capable of accurately analysing protein content of millet grains, with root mean square error (RMSEP) values for milled and intact grains of approximately 0.5%. Two PLS-R models of handheld instruments also yielded good results for milled grains with RMSEP values of about 0.6%. The semi-automated multivariate data analysis showed some drawbacks compared to standard data processing software. For intact grains, however, similar results could be achieved.


Assuntos
Panicum/química , Proteínas de Plantas/análise , Análise de Dados , Grão Comestível/química , Análise dos Mínimos Quadrados , Análise Multivariada , Panicum/classificação , Espectrofotometria Infravermelho/instrumentação , Espectrofotometria Infravermelho/métodos
14.
J Perinat Med ; 47(7): 785-791, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31365346

RESUMO

Background Human milk is the optimal source of nutrition for preterm infants. However, breast milk alone is often not sufficient to satisfy the high nutritional needs for growth and development in preterm infants. Fortified human breast milk is the best way to meet the nutritional needs of preterm infants. Human breast milk is fortified according to the estimated nutrient content of mature breast milk; however, because the content of breast milk is highly variable, the macronutrient support may be more or less than needed. The goal of this study was to analyze the macronutrient content of preterm human milk during the first 6 weeks of lactation. Methods The study included 32 mothers of preterm infants with a gestational age of ≤32 weeks. Breast milk was collected in 24-h cycles and analyzed daily using mid-infrared (MIR) spectroscopy. We measured protein, fat and lactose concentrations in the breast milk, and the energy content was calculated. Results The protein content was high during the first weeks of lactation, but decreased as lactation progressed. The fat, energy and lactose contents of the breast milk were low during the first 2 weeks of lactation, increased as lactation progressed and remained constant thereafter. In women with high body mass index (BMI), higher protein levels were found in transitional milk. In women who had high income level, higher fat and energy levels were found in transitional milk. Conclusion Our findings indicate that the macronutrient content of preterm breast milk changes throughout the course of lactation, with BMI and income level. Knowledge of the macronutrient composition of breast milk is necessary to ensure that preterm infants receive the appropriate types and quantities of nutrients to promote optimal growth, and to ensure that breast milk is fortified according to individual needs. Our findings may be useful for the provision of optimal nutritional support for preterm infants.


Assuntos
Aleitamento Materno , Fenômenos Fisiológicos da Nutrição do Lactente/fisiologia , Recém-Nascido Prematuro/crescimento & desenvolvimento , Lactação/fisiologia , Leite Humano/química , Nutrientes/análise , Índice de Massa Corporal , Aleitamento Materno/métodos , Aleitamento Materno/estatística & dados numéricos , Correlação de Dados , Ingestão de Energia/fisiologia , Feminino , Alimentos Fortificados , Humanos , Renda/estatística & dados numéricos , Recém-Nascido , Gravidez , Espectrofotometria Infravermelho/métodos
15.
J Am Soc Mass Spectrom ; 30(9): 1758-1767, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31286444

RESUMO

Gas-phase conformations of the sodium-cationized forms of the 2'-deoxycytidine and cytidine mononucleotides, [pdCyd+Na]+ and [pCyd+Na]+, are examined by infrared multiple photon dissociation action spectroscopy. Complimentary electronic structure calculations at the B3LYP/6-311+G(2d,2p)//B3LYP/6-311+G(d,p) level of theory provide candidate conformations and their respective predicted IR spectra for comparison across the IR fingerprint and hydrogen-stretching regions. Comparisons of the predicted IR spectra and the measured infrared multiple photon dissociation action spectra provide insight into the impact of sodium cationization on intrinsic mononucleotide structure. Further, comparison of present results with those reported for the sodium-cationized cytidine nucleoside analogues elucidates the impact of the phosphate moiety on gas-phase structure. Across the neutral, protonated, and sodium-cationized cytidine mononucleotides, a preference for stabilization of the phosphate moiety and nucleobase orientation is observed, although the details of this stabilization differ with the state of cationization. Several low-energy conformations of [pdCyd+Na]+ and [pCyd+Na]+ involving several different orientations of the phosphate moiety and sugar puckering modes are observed experimentally.


Assuntos
Citidina/química , DNA/química , RNA/química , Sódio/química , Espectrofotometria Infravermelho/métodos , Cátions Monovalentes/química , Citidina Monofosfato/química , Desoxicitidina Monofosfato/química , Gases/química , Conformação de Ácido Nucleico
16.
Analyst ; 144(16): 4826-4834, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31290490

RESUMO

This study demonstrates a unique strategy for enhancing infrared (IR) spectroscopic discrimination between gall bladder (GB) polyps and cancer. This strategy includes the separation of raw bile juice into three sections of organic, aqueous, and amphiphilic phases and a cooperative combination of all IR spectral features of each separated phase for the discrimination. Raw bile juice is viscous and complex in composition because it contains fatty acids, cholesterol, proteins, phospholipids, bilirubin, and other components; therefore, the acquisition of IR spectra providing more component-discernible information is fundamental for improving discrimination. For this purpose, raw bile juice was separated into an aqueous phase, mostly containing bile salts, an organic phase with isolated lipids, and an amphiphilic phase, mainly containing proteins. The subsequent IR spectra of each separated phase were mutually characteristic and complementary to each other. When all the IR spectral features were combined, the discrimination was improved compared to that using the spectra of raw bile juice with no separation. The cooperative integration of more component-specific spectra obtained from each separated phase enhanced the discrimination. In addition, the IR spectra of the major constituents in bile juice, such as bile acids, conjugated bile salts, lecithin, and cholesterol, were recorded to explain the IR features of each separated phase.


Assuntos
Bile/química , Neoplasias da Vesícula Biliar/diagnóstico , Pólipos/diagnóstico , Ácidos e Sais Biliares/análise , Colesterol/análise , Diagnóstico Diferencial , Vesícula Biliar , Humanos , Lecitinas/análise , Análise de Componente Principal , Espectrofotometria Infravermelho/métodos
17.
J Dairy Sci ; 102(10): 8907-8918, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31351717

RESUMO

The objective of this study was to compare mid-infrared reflectance spectroscopy (MIRS) analysis of milk and near-infrared reflectance spectroscopy (NIRS) analysis of feces with regard to their ability to predict the dry matter intake (DMI) of lactating grazing dairy cows. A data set comprising 1,074 records of DMI from 457 cows was available for analysis. Linear regression and partial least squares regression were used to develop the equations using the following variables: (1) milk yield (MY), fat percentage, protein percentage, body weight (BW), stage of lactation (SOL), and parity (benchmark equation); (2) MIRS wavelengths; (3) MIRS wavelengths, MY, fat percentage, protein percentage, BW, SOL, and parity; (4) NIRS wavelengths; (5) NIRS wavelengths, MY, fat percentage, protein percentage, BW, SOL, and parity; (6) MIRS and NIRS wavelengths; and (7) MIRS wavelengths, NIRS wavelengths, MY, fat percentage, protein percentage, BW, SOL, and parity. The equations were validated both within herd using animals from similar experiments and across herds using animals from independent experiments. The accuracy of equations was greater for within-herd validation compared with across-herds validation. Across-herds validation was deemed the more suitable method to assess equations for robustness and real-world application. The benchmark equation was more accurate [coefficient of determination (R2) = 0.60; root mean squared error (RMSE) = 1.68 kg] than MIRS alone (R2 = 0.30; RMSE = 2.23 kg) or NIRS alone (R2 = 0.16; RMSE = 2.43 kg). The combination of the benchmark equation with MIRS (R2 = 0.64; RMSE = 1.59 kg) resulted in slightly superior fitting statistics compared with the benchmark equation alone. The combination of the benchmark equation with NIRS (R2 = 0.58; RMSE = 1.71 kg) did not result in a more accurate prediction equation than the benchmark equation. The combination of MIRS and NIRS wavelengths resulted in superior fitting statistics compared with either method alone (R2 = 0.36; RMSE = 2.15 kg). The combination of the benchmark equation and MIRS and NIRS wavelengths resulted in the most accurate equation (R2 = 0.68; RMSE = 1.52 kg). A further analysis demonstrated that Holstein-Friesian cows could predict the DMI of Jersey × Holstein-Friesian crossbred cows using both MIRS and NIRS. Similarly, the Jersey × Holstein-Friesian animals could predict the DMI of Holstein-Friesian cows using both MIRS and NIRS. The equations developed in this study have the capacity to predict DMI of grazing dairy cows. From a practicality perspective, MIRS in combination with variables in the benchmark equation is the most suitable equation because MIRS is currently used on all milk-recorded milk samples from dairy cows.


Assuntos
Bovinos , Dieta/veterinária , Herbivoria , Espectrofotometria Infravermelho/veterinária , Animais , Peso Corporal , Ingestão de Alimentos , Fezes/química , Feminino , Lactação , Análise dos Mínimos Quadrados , Modelos Lineares , Leite , Gravidez , Espectrofotometria Infravermelho/métodos
18.
Eur J Pharm Sci ; 138: 104994, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31302210

RESUMO

Dihydromyricetin (DMY), a flavanonol compound found as the most abundant and bioactive constituent in Ampelopsis grossedentata (Hand-Mazz) W.T. Wang, possesses numerous pharmacological activities, such as antioxidant, anti-inflammation, anticancer, anti-microbial, hypoglycemic and hypolipidemic effects, and so on. Recently, DMY shows a promising potential to develop as an agent for the prevention and treatment of Type 2 diabetes mellitus (T2DM). However, the low oral bioavailability of DMY was one of the special concerns to be resolved for its clinical applications. In this study, DMY phospholipid complex (DMY-HSPC COM) was prepared by the solvent evaporation technique and optimized with DMY combination ratio. Scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and Fourier transform infrared spectrophotometry (FT-IR) were carried to characterize the formation of DMY-HSPC COM. The particle size, zeta potential, drug loading and solubility of DMY-HSPC COM were further investigated. The phospholipid complex technology could significantly improve the solubility of DMY. Pharmacokinetic study results of DMY-HSPC COM in healthy SD rats and T2DM rats demonstrated that the oral bioavailability was significantly increased when compared with pure DMY as well, which could be attributed to the improvement of the aqueous solubility of the complex, absorption promotion and a probable decrease in intestinal and hepatic metabolism. In addition, when compared with healthy SD rats, pharmacokinetic parameters of pure DMY and DMY-HSPC COM showed significant difference in T2DM rats. Thus, phospholipid complex technology holds a promising potential for increasing the oral bioavailability of DMY.


Assuntos
Flavonóis/química , Fosfolipídeos/química , Animais , Disponibilidade Biológica , Varredura Diferencial de Calorimetria/métodos , Diabetes Mellitus Tipo 2/metabolismo , Masculino , Microscopia Eletrônica de Varredura/métodos , Tamanho da Partícula , Ratos , Ratos Sprague-Dawley , Solubilidade/efeitos dos fármacos , Espectrofotometria Infravermelho/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Difração de Raios X/métodos
19.
Biochemistry (Mosc) ; 84(Suppl 1): S124-S143, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31213199

RESUMO

Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia accompanied by the disruption of carbohydrate, lipid, and proteins metabolism and development of long-term microvascular, macrovascular, and neuropathic changes. This review presents the results of spectroscopic studies on the glycation of tissues and cell proteins in organisms with naturally developing and model diabetes and in vitro glycated samples in a wide range of electromagnetic waves, from visible light to terahertz radiation. Experiments on the refractometric measurements of glycated and oxygenated hemoglobin in broad wavelength and temperature ranges using digital holographic microscopy and diffraction tomography are discussed, as well as possible application of these methods in the diabetes diagnostics. It is shown that the development and implementation of multimodal approaches based on a combination of phase diagnostics with other methods is another promising direction in the diabetes diagnostics. The possibilities of using optical clearing agents for monitoring the diffusion of substances in the glycated tissues and blood flow dynamics in the pancreas of animals with induced diabetes have also been analyzed.


Assuntos
Diabetes Mellitus/diagnóstico por imagem , Hemoglobina A Glicada/ultraestrutura , Animais , Velocidade do Fluxo Sanguíneo , Glicosilação , Holografia/métodos , Humanos , Microscopia/métodos , Espectrofotometria Infravermelho/métodos , Espectroscopia Terahertz/métodos , Tomografia/métodos
20.
Int J Mol Sci ; 20(10)2019 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-31137900

RESUMO

Over the years, there have been many developments and advances in the field of integral membrane protein research. As important pharmaceutical targets, it is paramount to understand the mechanisms of action that govern their structure-function relationships. However, the study of integral membrane proteins is still incredibly challenging, mostly due to their low expression and instability once extracted from the native biological membrane. Nevertheless, milligrams of pure, stable, and functional protein are always required for biochemical and structural studies. Many modern biophysical tools are available today that provide critical information regarding to the characterisation and behaviour of integral membrane proteins in solution. These biophysical approaches play an important role in both basic research and in early-stage drug discovery processes. In this review, it is not our objective to present a comprehensive list of all existing biophysical methods, but a selection of the most useful and easily applied to basic integral membrane protein research.


Assuntos
Dicroísmo Circular/métodos , Difusão Dinâmica da Luz/métodos , Recuperação de Fluorescência Após Fotodegradação/métodos , Proteínas de Membrana/química , Animais , Humanos , Proteínas de Membrana/metabolismo , Espectrofotometria Infravermelho/métodos
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