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1.
J Colloid Interface Sci ; 606(Pt 2): 1823-1832, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34507173

RESUMO

HYPOTHESIS: The injection of air into the sample cell of an isothermal titration calorimeter containing a liquid provides a rich-in-information signal, with a periodic contribution arising from the creation, growing and release of bubbles. The identification and analysis of such contributions allow the accurate determination of the surface tension of the target liquid. EXPERIMENTS: Air is introduced at a constant rate into the sample cell of the calorimeter containing either a pure liquid or a solution. The resulting calorimetric signal is analyzed by a new algorithm, which is implemented into a computational code. FINDINGS: The thermal power generated by our experiments is often noisy, thus hiding the periodic signal arising from the bubbles' formation and release. The new algorithm was tested with a range of different types of calorimetric raw data, some of them apparently being just noise. In all cases, the contribution of the bubbles to the signal was isolated and the corresponding period was successfully determined in an automated way. It is also shown that two reference measurements suffice to calibrate the instrument at a given temperature, regardless the injection rate, allowing the direct determination of surface tension values for the liquid contained in the sample cell.


Assuntos
Algoritmos , Calorimetria , Tensão Superficial , Temperatura , Termodinâmica
2.
Igaku Butsuri ; 41(3): 134-142, 2021.
Artigo em Japonês | MEDLINE | ID: mdl-34744124

RESUMO

A calibration service using a medical accelerator has been launched to calibrate a radiotherapy dosimeter in terms of an absorbed dose to water. The radiotherapy dosimeter calibrated by the calibration service can measure the absorbed dose to water without a beam quality conversion factor. In this paper, an overview of the calibration service for a high-energy photon beam and a high-energy electron beam was described, as well as methods of absorbed dose measurement and cross-calibration using the calibrated radiotherapy dosimeter. And the development status of a dose standard for a particle beam was reported.


Assuntos
Dosímetros de Radiação , Radiometria , Calibragem , Calorimetria , Aceleradores de Partículas , Fótons , Radioterapia de Alta Energia , Água
3.
Anal Chem ; 93(45): 14912-14917, 2021 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-34734709

RESUMO

Metal recognition by nucleic acids provides an intriguing route for biosensing of metal. Toward this goal, a key prerequisite is the acquisition of nucleic acids that can selectively respond to specific metals. Herein, we report for the first time the discovery of two small DNAs that can specifically bind Ni2+ and discriminate against similar ions, particularly, Co2+. Their minimal effective constructs are 60-70 nucleotides (nt) in length with Ni2+ binding even at harsh denaturing conditions of 8 M urea and 50 mM EDTA. Using isothermal titration calorimetry (ITC), we estimated the dissociation constant (KD) of a representative DNA to be 24.0 ± 4.5 µM, with a 9:1 stoichiometry of Ni2+ bound to DNA. As being engineered into nanosized particles, these DNAs can act like nanosponges to specifically adsorb Ni2+ from artificial wastewater, demonstrating their potential as a novel molecular tool for high-quality nickel enrichment and detection.


Assuntos
Metais , Níquel , Calorimetria , DNA
4.
J Vis Exp ; (175)2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34605810

RESUMO

The hazards associated with lithium-based battery chemistries are well-documented due to their catastrophic nature. Risk is typically qualitatively assessed through an engineering risk matrix. Within the matrix, potentially hazardous events are categorized and ranked in terms of severity and probability to provide situational awareness to decision makers and stakeholders. The stochastic nature of battery failures, particularly the lithium-ion chemistry, makes the probability axis of a matrix difficult to properly assess. Fortunately, characterization tools exist, such as accelerated rate calorimetry (ARC), that characterize degrees of battery failure severity. ARC has been used extensively to characterize reactive chemicals but can provide a new application to induce battery failures under safe, controlled experimental conditions and quantify critical safety parameters. Due to the robust nature of the extended volume calorimeter, cells may be safely taken to failure due to a variety of abuses: thermal (simple heating of cell), electrochemical (overcharge), electrical (external short circuit), or physical (crush or nail penetration). This article describes the procedures to prepare and instrument a commercial lithium-ion battery cell for failure in an ARC to collect valuable safety data: onset of thermal runaway, endotherm associated with polymer separator melting, pressure release during thermal runaway, gaseous collection for analytical characterization, maximum temperature of complete reaction, and visual observation of decomposition processes using a high temperature borescope (venting and cell can breach). A thermal "heat-wait-seek" method is used to induce cell failure, in which the battery is heated incrementally to a set point, then the instrument identifies heat generation from the battery. As heat generates a temperature rise in the battery, the calorimeter temperature follows this temperature rise, maintaining an adiabatic condition. Therefore, the cell does not exchange heat with the external environment, so all heat generation from the battery under failure is captured.


Assuntos
Fontes de Energia Elétrica , Lítio , Calorimetria , Temperatura Alta , Temperatura
5.
Mar Environ Res ; 172: 105510, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34717130

RESUMO

European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) are crucial species for the marine ecosystem of the Northwestern Mediterranean Sea. They account for a high percentage of fish landings and they represent an important economic income for the fishery sector. Concerns over their stock status are rising in recent years as biomass, growth, reproductive capacity, and body condition of both species are declining, with latitudinal variations. Therefore, there is an urgent need for a body condition monitoring scheme. Energy storage variability has important implications for both fish recruitment and population structure. Direct condition indices, such as energy density (ED) with bomb calorimetry, are highly reliable for measuring the energy content, but time-consuming. Alternatively, fatmeter analysis and relative condition index (Kn) have been proposed as effective indirect methods. The aim of this study is to test the application of fatmeter as a surrogate of bomb calorimetry to infer the energy content of sardine and anchovy. To validate its use, fatmeter values were compared with both ED and Kn values. Individuals of both species were sampled monthly for a year in order to assess seasonal variations in energy content. Our results highlight that fatmeter measurements are strongly correlated with calorimetry ED for sardine, while a weaker but significant correlation was found for anchovy. The observed differences between the two species are related to their breeding strategies. Based on this study, Kn cannot be considered a good proxy of the energy density of sardine, in particular during the resting period. By contrast, fatmeter analysis appears to be a faster and suitable method to evaluate the energy content of both species routinely. In addition, we provide a linear model to infer ED from fatmeter values for both small pelagic fish. Eventually, these findings could be used to implement body condition monitoring protocols and boost continuous large-scale monitoring.


Assuntos
Ecossistema , Peixes , Animais , Calorimetria , Pesqueiros , Humanos , Alimentos Marinhos
6.
Anal Bioanal Chem ; 413(29): 7251-7263, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34622322

RESUMO

Supply shortage for the development and production of preventive, therapeutic, and diagnosis tools during the COVID-19 pandemic is an important issue affecting the wealthy and poor nations alike. Antibodies and antigens are especially needed for the production of immunological-based testing tools such as point-of-care tests. Here, we propose a simple and quick magnetic nanoparticle (MNP)-based separation/isolation approach for the repurposing of infected human samples to produce specific antibodies and antigen cocktails. Initially, an antibody cocktail was purified from serums via precipitation and immunoaffinity chromatography. Purified antibodies were conjugated onto MNPs and used as an affinity matrix to separate antigens. The characterization process was performed by ELISA, SDS-PAGE, electrochemistry, isothermal titration calorimetry, and LC-Q-TOF-MS/MS analyses. The MNP-separated peptides can be used for mass spectrometry-based as well as paper-based lateral flow assay diagnostic. The exploitation of the current workflow for the development of efficient diagnostic tools, specific treatments, and fundamental research can significantly impact the present or eventual pandemic. This workflow can be considered as a two birds, one stone-like strategy.


Assuntos
Anticorpos Antivirais/isolamento & purificação , Antígenos Virais/isolamento & purificação , COVID-19/diagnóstico , Análise Custo-Benefício , Imunoensaio/economia , SARS-CoV-2/isolamento & purificação , Viremia/virologia , Anticorpos Antivirais/sangue , Antígenos Virais/sangue , COVID-19/virologia , Calorimetria , Eletroforese em Gel de Poliacrilamida , Ensaio de Imunoadsorção Enzimática , Humanos , SARS-CoV-2/imunologia , Manejo de Espécimes , Espectrometria de Massas em Tandem , Viremia/sangue , Fluxo de Trabalho
7.
Nat Commun ; 12(1): 6244, 2021 10 29.
Artigo em Inglês | MEDLINE | ID: mdl-34716322

RESUMO

Biological degradation of Polyethylene terephthalate (PET) plastic and assimilation of the corresponding monomers ethylene glycol and terephthalate (TPA) into central metabolism offers an attractive route for bio-based molecular recycling and bioremediation applications. A key step is the cellular uptake of the non-permeable TPA into bacterial cells which has been shown to be dependent upon the presence of the key tphC gene. However, little is known from a biochemical and structural perspective about the encoded solute binding protein, TphC. Here, we report the biochemical and structural characterisation of TphC in both open and TPA-bound closed conformations. This analysis demonstrates the narrow ligand specificity of TphC towards aromatic para-substituted dicarboxylates, such as TPA and closely related analogues. Further phylogenetic and genomic context analysis of the tph genes reveals homologous operons as a genetic resource for future biotechnological and metabolic engineering efforts towards circular plastic bio-economy solutions.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Comamonas/genética , Ácidos Ftálicos/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Calorimetria , Comamonas/química , Comamonas/metabolismo , Cristalografia por Raios X , Fluorometria/métodos , Ligantes , Modelos Moleculares , Simulação de Acoplamento Molecular , Mutação , Óperon , Filogenia , Conformação Proteica , Xenobióticos/metabolismo
8.
Arch Biochem Biophys ; 713: 109045, 2021 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-34627750

RESUMO

The standard isothermal titration calorimetry (ITC) curve, characterized as a typical sigmoid is strictly confined by the so-called c value, which is a ratio of titrand concentration to KD. The proper c value with a range from 5 to 500 is commonly recommended as a standard protocol in routine detection process for acquiring the reliable fitting results in 1:1 binding mode. However, if the c value is less than "1" due to the weak binding or low concentration of analyte, fitting precision gets unstable and susceptible to the data noise. Herein, we first got a deep discussion into the reliability of the fitting procedure for 1:1 binding mode by data simulation, then quantized the effect of several affecting factors on the precision of parameters estimation through mathematical analysis. Finally, we proposed the value of 2~4 times KD for final ligand concentration is optimal for the ITC titration in low c system (c < 1). All the theoretical derivations were further verified by a practical experiment of Magnesium-EDTA binding test.


Assuntos
Calorimetria/estatística & dados numéricos , Ácido Edético/química , Cloreto de Magnésio/química , Termodinâmica
9.
Molecules ; 26(19)2021 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-34641288

RESUMO

In this paper, a novel antioxidant analysis is proposed using a simple minimized device based on moving drops as solution handling and a smartphone as a detector. This approach is based on the colorimetric determination of the scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•), expressed as the half-maximal inhibitory concentration (IC50), vitamin C equivalent antioxidant capacity (VCEAC), and Trolox equivalent antioxidant capacity (TEAC). A small drop of the positive control or the samples moves by eluting an ethanol drop down by the force of gravity to react with a DPPH• drop in the detection zone. The color change of DPPH• is monitored by a smartphone camera, and the color signals are processed using Adobe Photoshop software. The magenta-to-yellow ratio was successfully applied to evaluate the percentage of DPPH• inhibition with no significant difference compared with the reference spectrophotometric method at a confidence level of 95%. The total phenolic content (TPC) was measured using the Folin-Ciocalteu assay. An application to Miang (fermented tea leaf extract) showed the consonant relationship between the scavenging activity of DPPH• and TPC.


Assuntos
Antioxidantes/análise , Técnicas Biossensoriais/instrumentação , Ácido Ascórbico/análise , Calorimetria , Concentração Inibidora 50 , Fenóis/análise , Smartphone , Software
10.
Langmuir ; 37(40): 11781-11792, 2021 10 12.
Artigo em Inglês | MEDLINE | ID: mdl-34570499

RESUMO

A new proposal to obtain aggregation numbers from isothermal titration calorimetry dilution experiments is described and tested using dodecyl trimethyl ammonium bromide, dodecyl methylimidazolium chloride, dodecyl methylimidazolium sulfonate, and didecyl methylimidazolium chloride aqueous solutions at different temperatures. The results were compared to those obtained from fluorescence measurements and also with data from the literature. In addition to the aggregation number, the molar free energy to transfer a solute molecule from the aggregate to the bulk solution, the enthalpy corresponding to the formation of the self-assembled suprastructures, the molar heat corresponding to the dilution of monomers and aggregates, and an offset parameter to account for unpredictable external contributions are simultaneously obtained using the same method. The new equations are compared to those obtained from previous proposals, and they are also analyzed in detail to assess the impact of each fitting parameter in the profile of the calorimetric isotherm. This new approach has been implemented in a computational code that automatically determines the fitting parameters as well as the corresponding statistical uncertainties for the large variety of calorimetric profiles that have been tested. Given the high sensitivity of the dilution experiments to the aggregation number for relatively small assemblies, our approach is proposed also to quantify the oligomerization state of biomolecules such as proteins and peptides.


Assuntos
Micelas , Proteínas , Calorimetria , Soluções , Termodinâmica
11.
Anal Chem ; 93(37): 12698-12706, 2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34498849

RESUMO

Isothermal titration calorimetry (ITC) is a widely used method to determine binding affinities and thermodynamics in ligand-receptor interactions, but it also has the capability of providing detailed information on much more complex events. However, the lack of available methods to analyze ITC data is limiting the use of the technique in such multifaceted cases. Here, we present the software ANISPROU. Through a semi-empirical approach that allows for extraction of quantitative information from complex ITC data, ANISPROU solves an inverse problem where three parameters describing a set of predefined functions must be found. In analogy to strategies adopted in other scientific fields, such as geophysics, imaging, and many others, it employs an optimization algorithm which minimizes the difference between calculated and experimental data. In contrast to the existing methods, ANISPROU provides automated and objective analysis of ITC data on sodium dodecyl sulfate (SDS)-induced protein unfolding, and in addition, more information can be extracted from the data. Here, data series on SDS-mediated protein unfolding is analyzed, and binding isotherms and thermodynamic information on the unfolding events are extracted. The obtained binding isotherms as well as the enthalpy of different events are similar to those obtained using the existing manual methods, but our methodology ensures a more robust result, as the entire data set is used instead of single data points. We foresee that ANISPROU will be useful in other cases with complex enthalpograms, for example, in cases with coupled interactions in biomolecular, polymeric, and amphiphilic systems including cases where both structural changes and interactions occur simultaneously.


Assuntos
Tensoativos , Calorimetria , Ligantes , Ligação Proteica , Dodecilsulfato de Sódio , Termodinâmica
12.
Anal Chem ; 93(37): 12723-12732, 2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34514786

RESUMO

There is growing interest in using isothermal titration calorimetry (ITC) to characterize enzyme kinetics by measuring the heat produced or absorbed by catalysis in real time. Since virtually all chemical reactions are associated with changes in enthalpy, ITC represents a robust and nearly universal experimental approach. Nevertheless, there are technical challenges that limit ITC's applicability. For instance, the full kinetic characterization of enzymes with two substrates (bi-substrate enzymes), which comprise the majority of known examples, requires a series of experiments to be performed as the concentrations of both substrates are varied. This is a time-consuming and expensive process using current ITC methods since many (>5) individual experiments must be performed independently to obtain a sufficient quantity of data. We have developed a new ITC method, which we term 2D-ITC, which maps the reaction velocity as a function of two substrate concentrations in a single, roughly 2 h long experiment. This method provides a level of detail that rivals or exceeds any existing enzyme assay, as a single experiment generates on the order of 7000 catalytic rate measurements. In a proof-of-principle application to rabbit muscle pyruvate kinase (rMPK), the method correctly identified the enzyme's random sequential mechanism and allosteric catalytic suppression by the amino acid phenylalanine (Phe). Unexpectedly, we found that while Phe reduces affinity for the substrate phosphoenolpyruvate, a known phenomenon, it also alleviates inhibition by the reaction product ATP, which had not been reported previously. Given the relative abundance of ATP in the cell, this opposing effect is expected to have a substantial impact on rMPK activity.


Assuntos
Ensaios Enzimáticos , Animais , Calorimetria , Catálise , Cinética , Coelhos , Termodinâmica
13.
Langmuir ; 37(37): 11176-11187, 2021 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-34499515

RESUMO

The study of the interactions of drug molecules with genetic materials plays a key role underlying the development of new drugs for many life-threatening diseases in pharmaceutical industries. Understanding their fundamental base-specific and/or groove-binding interaction is crucial to target the genetic material with an external drug, which can pave the way to curing diseases related to the genetic material. Here, we studied the interaction of cryptolepine hydrate (CRYP) with RNA under physiological conditions knowing the antimalarial and anticancer activities of the drug. Our experiments explicitly demonstrate that CRYP interacts with the guanine- and adenine-rich region within the RNA duplex. The pivotal role of the hydrophobic interaction governing the interaction is substantiated by temperature-dependent isothermal titration calorimetry experiments and spectroscopic studies. Circular dichroism study underpins a principally intercalative mode of binding of CRYP with RNA. This interaction is found to be drastically affected in the presence of magnesium salt, which has a strong propensity to coordinate with RNA nucleobases, which can in turn modulate the interaction of the drug with RNA. The temperature-dependent calorimetric results substantiate the occurrence of entropy-enthalpy compensation, which enabled us to rule out the possibility of groove binding of the drug with RNA. Furthermore, our results also show the application of host-guest chemistry in sequestering the RNA-bound drug, which is crucial to the development of safer therapeutic applications.


Assuntos
RNA , Calorimetria , Dicroísmo Circular , Interações Hidrofóbicas e Hidrofílicas , Alcaloides Indólicos , Quinolinas , RNA/genética , Termodinâmica
14.
Sci Rep ; 11(1): 17849, 2021 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-34497320

RESUMO

Known as metabolic flexibility, oxidized substrate is selected in response to changes in the nutritional state. Sleep imposes an extended duration of fasting, and oxidized substrates during sleep were assumed to progressively shift from carbohydrate to fat, thereby gradually decreasing the respiratory quotient (RQ). Contrary to this assumption, whole-room indirect calorimetry with improved time resolution revealed that RQ re-ascended prior to awakening, and nadir of RQ in non-obese young adults occurred earlier in women than men after bedtime. The transient decrease in RQ during sleep was blunted in metabolically inflexible men with smaller amplitude of diurnal rhythm in RQ. Similarly, the effect of 10 years difference in age on RQ became significant during sleep; the decrease in RQ during sleep was blunted in older subjects. Inter-individual difference in RQ become apparent during sleep, and it might serve as a window to gain insight into the early-stage pathogenesis of metabolic inflexibility.


Assuntos
Glicemia/metabolismo , Temperatura Corporal/fisiologia , Metabolismo Energético/fisiologia , Sono/fisiologia , Fatores Etários , Calorimetria , Ingestão de Energia/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Adulto Jovem
15.
J Biol Chem ; 297(4): 101151, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34478710

RESUMO

The seasonal nature of outbreaks of respiratory viral infections with increased transmission during low temperatures has been well established. Accordingly, temperature has been suggested to play a role on the viability and transmissibility of SARS-CoV-2, the virus responsible for the COVID-19 pandemic. The receptor-binding domain (RBD) of the Spike glycoprotein is known to bind to its host receptor angiotensin-converting enzyme 2 (ACE2) to initiate viral fusion. Using biochemical, biophysical, and functional assays to dissect the effect of temperature on the receptor-Spike interaction, we observed a significant and stepwise increase in RBD-ACE2 affinity at low temperatures, resulting in slower dissociation kinetics. This translated into enhanced interaction of the full Spike glycoprotein with the ACE2 receptor and higher viral attachment at low temperatures. Interestingly, the RBD N501Y mutation, present in emerging variants of concern (VOCs) that are fueling the pandemic worldwide (including the B.1.1.7 (α) lineage), bypassed this requirement. This data suggests that the acquisition of N501Y reflects an adaptation to warmer climates, a hypothesis that remains to be tested.


Assuntos
Enzima de Conversão de Angiotensina 2/metabolismo , SARS-CoV-2/metabolismo , Glicoproteína da Espícula de Coronavírus/metabolismo , Enzima de Conversão de Angiotensina 2/química , COVID-19/patologia , COVID-19/virologia , Calorimetria , Humanos , Interferometria , Polimorfismo de Nucleotídeo Único , Ligação Proteica , Estrutura Quaternária de Proteína , SARS-CoV-2/isolamento & purificação , Glicoproteína da Espícula de Coronavírus/química , Temperatura , Termodinâmica
16.
J Phys Chem Lett ; 12(38): 9384-9390, 2021 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-34551250

RESUMO

Interactions of biomolecules with inorganic oxide surfaces such as silica in aqueous solutions are of profound interest in various research fields, including chemistry, biotechnology, and medicine. While there is a general understanding of the dominating electrostatic interactions, the binding mechanism is still not fully understood. Here, chromatographic zonal elution and flow microcalorimetry experiments were combined with molecular dynamic simulations to describe the interaction of different capped amino acids with the silica surface. We demonstrate that ion pairing is the dominant electrostatic interaction. Surprisingly, the interaction strength is more dependent on the repulsive carboxy group than on the attracting amino group. These findings are essential for conducting experimental and simulative studies on amino acids when transferring the results to biomolecule-surface interactions.


Assuntos
Alanina/química , Arginina/química , Dióxido de Silício/química , Alanina/metabolismo , Arginina/metabolismo , Calorimetria , Simulação de Dinâmica Molecular , Dióxido de Silício/metabolismo , Eletricidade Estática , Propriedades de Superfície
17.
AAPS PharmSciTech ; 22(7): 232, 2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34468866

RESUMO

Cyclodextrin (CD) complexes are frequently used for enhancing the solubility or absorption of poorly water-soluble drugs. On the contrary, little is known about their complex formation with water-soluble drugs. Here, we have studied the interaction between 2-hydroxypropyl ß-CD (HPßCD) and three water-soluble drugs, namely naloxone (NX), oxycodone (OC), and tramadol (TR), by isothermal titration calorimetry (ITC) combined with molecular modeling in view of the potential impact on drug release. The results showed that the complex formation of HPßCD with all three drugs occurs spontaneously. The complexes formed with NX and OC were found to be 2NX:1HPßCD and 3OC:2HPßCD, respectively. TR was found to form 2 complexes with HPßCD; of 1:2 and 1:1 complexation ratios. The binding of HPßCD to NX was greater than to OC due to the higher hydrophobicity of the structure of the former. Moreover, the binding affinity of HPßCD to TR was higher than to OC, which indicated the effect of the higher flexibility of the guest in increasing the binding affinity. In vitro drug release experiments from the various complexes revealed a significant impact of the stoichiometry of the complex on the release profiles. Accordingly, the co-administration of cyclodextrins with water-soluble drugs should be closely monitored, as it may result in unintentional complex formation that can potentially impact the drugs' gastrointestinal absorption.


Assuntos
Ciclodextrinas , Preparações Farmacêuticas , beta-Ciclodextrinas , 2-Hidroxipropil-beta-Ciclodextrina , Calorimetria , Solubilidade , Água
18.
Chem Commun (Camb) ; 57(74): 9370-9373, 2021 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-34528955

RESUMO

Herein, a framework for the estimation of the thermodynamic properties of molecular crystals via the refinement of frequencies from density functional theory calculations against X-ray diffraction data is presented. The framework provides an efficient approach to including the contribution of acoustic modes in the thermodynamic properties. The obtained heat capacities for urea, the α- and ß-glycine polymorphs, benzoic acid, and 4'-hydroxyacetophenone are in good agreement with those from adiabatic calorimetry.


Assuntos
Acetofenonas/química , Ácido Benzoico/química , Teoria da Densidade Funcional , Glicina/química , Calorimetria , Termodinâmica , Difração de Raios X
19.
Molecules ; 26(16)2021 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-34443491

RESUMO

Glycyrrhetic acid (GA) and stearyl glycyrrhetinate (SG) are two interesting compounds from Glycyrrhiza glabra, showing numerous biological properties widely applied in the pharmaceutical and cosmetic fields. Despite these appreciable benefits, their potential therapeutic properties are strongly compromised due to unfavourable physical-chemical features. The strategy exploited in the present work was to develop solid lipid nanoparticles (SLNs) as carrier systems for GA and SG delivery. Both formulations loaded with GA and SG (GA-SLNs and SG-SLNs, respectively) were prepared by the high shear homogenization coupled to ultrasound (HSH-US) method, and we obtained good technological parameters. DSC was used to evaluate their thermotropic behaviour and ability to act as carriers for GA and SG. The study was conducted by means of a biomembrane model (multilamellar vesicles; MLVs) that simulated the interaction of the carriers with the cellular membrane. Unloaded and loaded SLNs were incubated with the biomembranes, and their interactions were evaluated over time through variations in their calorimetric curves. The results of these studies indicated that GA and SG interact differently with MLVs and SLNs; the interactions of SG-SLNs and GA-SLNs with the biomembrane model showed different variations of the MLVs calorimetric curve and suggest the potential use of SLNs as delivery systems for GA.


Assuntos
Calorimetria , Ácido Glicirretínico/análogos & derivados , Ácido Glicirretínico/farmacologia , Lipídeos/química , Nanopartículas/química , Ácido Glicirretínico/química , Cinética , Membranas , Eletricidade Estática , Temperatura de Transição
20.
J Phys Chem B ; 125(34): 9719-9726, 2021 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-34415161

RESUMO

Measurements of the thermodynamic properties of biomolecular folding (ΔG°, ΔH°, ΔS°, etc.) provide a wealth of information on the folding process and have long played a central role in biophysical investigation. In particular, the excess heat capacity of folding (ΔCP) is crucial, as typically measured in bulk ensemble studies by differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). Here, we report the first measurements of ΔCP at the single-molecule level using the single-molecule fluorescence resonance energy transfer (smFRET) as well as the very first measurements of the heat capacity change associated with achieving the transition state (ΔC‡P) for nucleic acid folding. The deoxyribonucleic acid (DNA) hairpin used in these studies exhibits an excess heat capacity for hybridization (ΔCP = -340 ± 60 J/mol/K per base pair) consistent with the range of literature expectations (ΔCP = -100 to -420 J/mol/K per base pair). Furthermore, the measured activation heat capacities (ΔC‡P) for such hairpin unfolding are consistent with a folding transition state containing few fully formed base pairs, in agreement with prevailing models of DNA hybridization.


Assuntos
DNA , Temperatura Alta , Calorimetria , Varredura Diferencial de Calorimetria , Termodinâmica
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