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1.
Opt Express ; 32(6): 10461-10478, 2024 Mar 11.
Artículo en Inglés | MEDLINE | ID: mdl-38571257

RESUMEN

We propose a multimode interference-based optical fiber NHTSN sensor with a helical taper for simultaneous measurement of micro torsion and temperature. The sensor consists of single mode fiber (SMF), no-core fiber (NCF), and seven-core fiber (SCF). A helical taper is fabricated in the SCF using a flame heater, forming the SMF-NCF-Helical Taper SCF-NCF-SMF (NHTSN) structure. Theoretical analysis and experimental results demonstrate that the introduction of helical taper not only imparts directionality to the torsion measurement, but also results in a significant improvement in torsion sensitivity due to the increased inter-mode optical path difference (OPD) and enhanced inter-mode coupling. In the experiment, the torsion sensitivity of the NHTSN sensor reaches -1.255 nm/(rad/m) in the twist rate (TR) range of -3.931 rad/m to 3.931 rad/m, which is a 9-fold improvement over the original structure. Further reduction of the helical taper diameter increases the sensitivity to -1.690 nm/(rad/m). In addition, the sensor has a temperature sensitivity of up to 97 pm/°C from 20 °C to 90 °C, and simultaneous measurement of torsion and temperature is attainable through a dual-parameter measurement matrix. The NHTSN sensor possesses advantages of compact size, high sensitivity, good linearity, and strain-independence, endowing it with potential applications in structural health monitoring (SHM) and engineering machinery.

2.
J Fluoresc ; 2024 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-38193953

RESUMEN

A fluorescent Fe3+ probe ((C10H7NO2)2B18H20, M1) by introducing two isoquinoline-1-carboxylic acid group into the 6,9-position of anti-B18H22 was designed and synthesized. The structure of M1 was investigated by 1H NMR, MS, FT-IR and theoretical calculation, and its optical properties were characterized with UV-Vis and PL. M1 showed aggregation induced emission enhancement (AIEE) properties in THF/H2O solution, and exhibited an excellent selectivity toward Fe3+ in THF/H2O (v/v, ƒw = 95%) solution with a detection limit of 1.93 × 10-5 M. The interaction mechanism of probe for detecting Fe3+ is attributed to the involvement of intramolecular charge transfer (ICT) process. Furthermore, a optical fiber fluorescent Fe3+ sensor based on M1 sensing film was developed, the detection limit of the optical fiber Fe3+ fluorescent sensor could be improved to13.8 pM, the ultra-low detection limit is superior to most reported fluorescent probes (or sensors) towards Fe3+. This method has the advantages of high sensitivity, anti-interference and easy to operate, and has great potential in the field of the analysis of environmental and biological samples.

3.
Int J Mol Sci ; 25(9)2024 Apr 25.
Artículo en Inglés | MEDLINE | ID: mdl-38731917

RESUMEN

Proton magnetic resonance spectroscopy (1H MRS) presents a powerful tool for revealing molecular-level metabolite information, complementary to the anatomical insight delivered by magnetic resonance imaging (MRI), thus playing a significant role in in vivo/in vitro biological studies. However, its further applications are generally confined by spectral congestion caused by numerous biological metabolites contained within the limited proton frequency range. Herein, we propose a pure-shift-based 1H localized MRS method as a proof of concept for high-resolution studies of biological samples. Benefitting from the spectral simplification from multiplets to singlet peaks, this method addresses the challenge of spectral congestion encountered in conventional MRS experiments and facilitates metabolite analysis from crowded NMR resonances. The performance of the proposed pure-shift 1H MRS method is demonstrated on different kinds of samples, including brain metabolite phantom and in vitro biological samples of intact pig brain tissue and grape tissue, using a 7.0 T animal MRI scanner. This proposed MRS method is readily implemented in common commercial NMR/MRI instruments because of its generally adopted pulse-sequence modules. Therefore, this study takes a meaningful step for MRS studies toward potential applications in metabolite analysis and disease diagnosis.


Asunto(s)
Encéfalo , Espectroscopía de Protones por Resonancia Magnética , Animales , Porcinos , Espectroscopía de Protones por Resonancia Magnética/métodos , Encéfalo/metabolismo , Encéfalo/diagnóstico por imagen , Imagen por Resonancia Magnética/métodos , Vitis/química , Fantasmas de Imagen
4.
Opt Express ; 30(2): 1152-1166, 2022 Jan 17.
Artículo en Inglés | MEDLINE | ID: mdl-35209281

RESUMEN

We have manufactured an intensity modulated optical fiber SMDMS sensor with hydroxyethyl cellulose (HEC) hydrogel coating for simultaneous measurement of RH and temperature. The SMDMS sensor was manufactured by splicing single-mode fiber (SMF), multi-mode fiber (MMF), dispersion compensation fiber (DCF), MMF, and SMF in sequence to form a structure of SMF + MMF + DCF + MMF + SMF (SMDMS). The cladding of MMFs and DCF were corroded by hydrofluoric acid (HF) and coated with HEC hydrogel to excite a strong evanescent field and increase the sensitivity of the SMDMS sensor. The adsorption of water molecules by HEC will cause a change in the effective refractive index of cladding mode, which will eventually change the intensity of the transmission spectrum. The experimental results indicate that the sensitivities are 0.507 dB/%RH and 0.345 dB/°C in the RH range of 30%-80% and temperature range of 10°C-50°C, respectively. At last, a dual-parameter measurement matrix is constructed based on the experimental results to achieve the simultaneous measurement of RH and temperature. The SMDMS sensor has the advantages of high sensitivity and good robustness, and has potential application prospects in daily life and other fields.

5.
Opt Express ; 30(17): 30936-30948, 2022 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-36242188

RESUMEN

Metasurface based on independent and simultaneous control of near field and far field has significant potential for use in multichannel optics platform devices. However, the previous studies cannot satisfy independent and simultaneous control of near field and far field under a single line source, which made a significant challenge to multichannel optical platforms working in a compact environment. To manipulate effectively and freely the amplitude and phase of transmission under line source, Marius' law and Propagation phase was introduced on all-dielectric encoding metasurfaces meta-atoms. The Marius' law and Propagation phase can control the size and rotation angle of meta-atoms to encode grayscale amplitude images and holographic phase images. Finite-difference time-domain simulation results reveal that dual channel metasurface under a single line source achieves the same display effect as the dual channel metasurface under multiple light sources, which proves the feasibility of our studies. Moreover, under different angles of the line source, we encode the near-field binary image by using the degeneracy rotation angle of meta-atoms. Finally, a three-channel metasurface was obtained without affecting the display of the previous two-channel metasurface. As a result, the independent control amplitude, phase, and polarization of the incident light wave were achieved. The proposed metasurface could be applied in creating a multi-channel metasurface optical platform in a compact environment, which has application potential in image displays, optical storage, optical anti-counterfeiting, and information encryption technology.

6.
Opt Express ; 30(26): 47216-47234, 2022 Dec 19.
Artículo en Inglés | MEDLINE | ID: mdl-36558655

RESUMEN

In this paper, an asymmetric structure optical fiber sensor is proposed to measure relative humidity (RH). The sensing structure is composed of splicing dispersion compensation fiber (DCF) and coreless fiber (NCF), and two sections of single-mode fiber (SMF) at both ends. Peanut shaped structure is used as a beam splitter at the input side, and the NCF is used as a beam combiner at the output side to form interference fringes. The partial cladding of DCF was etched, and polyvinyl alcohol (PVA) was coated on the etched area to form a hygroscopic film. When the ambient humidity changes, the refractive index and thickness of the hygroscopic film will change, which will lead to the wavelength shift of the resonant dip. The experimental results show that the sensitivity of the sensor is 0.1304 nm/RH% and 0.4452 nm/RH% in the RH range of 55%-75% and 75%-95%, respectively. In order to improve the sensitivity further, the original spectrum data is filtered by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT), and the high-frequency interference components of high-order mode (LP09) and fundamental mode are obtained, which is superimposed with a simulated signal to form Vernier effect. With the method of virtual Vernier effect, the sensitivity in the RH range of 55%-75% is improved to 2.869 nm/RH%, which is 22 times larger than the original sensitivity, and the sensitivity in the RH range of 75%-95% is improved to 2.64 nm/RH%, which is 6 times larger than the original sensitivity.

7.
Opt Express ; 29(15): 24102-24117, 2021 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-34614661

RESUMEN

A single core-offset Mach-Zehnder interferometer (MZI) coated with polyvinyl alcohol (PVA) for simultaneous measurement of relative humidity (RH) and temperature is proposed in this paper. The sensing structure is fabricated by splicing dispersion compensating fiber (DCF) and no-core fiber (NCF) and splicing two single-mode fibers (SMF) at both ends, where the core-offset is located at the splicing of SMF and DCF. A part of the cladding of DCF is etched to excite the high-order cladding mode (LP10), and PVA is coated on the etched area. The refractive index of PVA varies due to the adsorption of water molecules. Therefore, when the ambient relative humidity and temperature change, the change of MZI phase difference causes the wavelength of the resonant dip to shift. The experimental results indicate that the proposed sensor has a sensitivity of 0.256 nm/RH% for RH range of 30%-95%, and a sensitivity of 0.153 nm/℃ for temperature range of 20℃-80℃, respectively. The simultaneous measurement of RH and temperature can be achieved by demodulating the sensitivity coefficient matrix. The proposed sensor has the characteristics of good repeatability, high sensitivity, and good stability, which make it potentially applications for the detection of RH and temperature measurement.

8.
Sensors (Basel) ; 21(11)2021 Jun 04.
Artículo en Inglés | MEDLINE | ID: mdl-34199927

RESUMEN

A graphene oxide-coated in-fiber Mach-Zehnder interferometer (MZI) formed with a multimode fiber-thin core fiber-multimode fiber (MMF-TCF-MMF) is proposed and experimentally demonstrated for ammonia gas (NH3) sensing. The MZI structure is composed of two segments of MMF of length 2 mm, with a flame-tapered TCF between them as the sensing arm. The MMFs act as mode couplers to split and recombine light owing to the core diameter mismatch with the other fibers. A tapered TCF is formed by the flame melting taper method, resulting in evanescent wave leakage. A layer of graphene oxide (GO) is applied to the tapered region of the TCF to achieve gas adsorption. The sensor operates on the principle of changing the effective refractive index of the cladding mode of a fiber through changing the conductivity of the GO coating by adsorbed NH3 molecules, which gives rise to a phase shift and shows as the resonant dip shifts in the transmission spectrum. So the concentration of the ammonia gas can be obtained by measuring the dip shift. A wavelength-shift sensitivity of 4.97 pm/ppm with a linear fit coefficient of 98.9% is achieved for ammonia gas concentrations in the range of 0 to 151 ppm. In addition, we performed a repetitive dynamic response test on the sensor by charging/releasing NH3 at concentration of 200 ppm and a relative humidity test in a relative humidity range of 35% to 70%, which demonstrates the reusability and stability of the sensor.

9.
Pediatr Dermatol ; 35(1): 121-125, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-29243341

RESUMEN

BACKGROUND/OBJECTIVE: To report our observations from a trial of the short-term effectiveness and safety of topical carteolol hydrochloride drops to treat infantile hemangiomas (IHs). METHODS: From October 2012 to September 2015, the study recruited 349 children with superficial IHs. Participants were randomized to two groups: treatment (n = 224 who received 2% carteolol hydrochloride drops administered to the lesion surface twice daily) and observation (n = 125 who did not receive treatment). Therapy duration was 6 months. RESULTS: The mean age at the beginning of treatment was 3.2 months. Treatment responses were categorized as class 1 (total regression), class 2 (partial regression or controlled growth), or class 3 (no response). Of infants receiving carteolol treatment, 10.7% (24 patients) were categorized as class 1, 72.3% (162 patients) as class 2, and 17.0% (38 patients) as class 3. Of infants in the observation group, 5.6% (7 patients) were categorized as class 1, 25.6% (32 patients) as class 2, and 68.8% (86 patients) as class 3. No adverse effects were noted during treatment. CONCLUSION: Carteolol is an effective, safe topical treatment for superficial IHs. Carteolol may be used to treat proliferative superficial IHs, particularly in infants younger than 6 months.


Asunto(s)
Antagonistas Adrenérgicos beta/administración & dosificación , Carteolol/administración & dosificación , Hemangioma/tratamiento farmacológico , Administración Tópica , Pueblo Asiatico , Femenino , Humanos , Lactante , Masculino , Estudios Prospectivos , Resultado del Tratamiento , Espera Vigilante
10.
Anal Chem ; 89(23): 12646-12651, 2017 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-29110456

RESUMEN

Two-dimensional (2D) J-resolved NMR technique offers a natural solution for disentangling complex mixtures that suffer from crowded spectra in 1D NMR. The applicability of classical 2D J-resolved spectroscopy is inevitably limited by phase-twist lineshapes and strong coupling artifacts. Here, a general and robust NMR method is proposed to record 2D absorption-mode J-resolved spectra in rapid acquisition manner. This method can also reduce the impact of strong coupling artifacts, thus achieving full considerations for applications. Intuitively, this method delivers pure chemical shifts along one dimension and orthogonally adds J couplings along the other dimension, free of 45° spectral shearing. It may provide a powerful tool for structural and configurational studies as well as biological analyses.

11.
Anal Chem ; 89(13): 7115-7122, 2017 07 05.
Artículo en Inglés | MEDLINE | ID: mdl-28581726

RESUMEN

NMR spectroscopy is a commonly used analytical technique in practical applications, and its applicability is further promoted by pure chemical shift techniques based on spectral simplification for analyses. Unfortunately, magnetic field inhomogeneity caused by adverse experimental conditions remains an obstacle restricting NMR applications. In this study, we introduce a new NMR method for high-resolution pure shift proton (1H) NMR measurements in inhomogeneous magnetic fields. We demonstrate that the method allows one to perform chemical analyses on complex solutions in deshimmed magnetic fields, to obtain metabolite information on intact biological tissues with intrinsic field inhomogeneities and to achieve in situ electrochemical detection under externally adverse field conditions. This approach is readily implemented on common commercial NMR instruments without field shimming and locking procedures, specialized hardware requirements as well as complicated sample pretreatments. It provides an effective tool for NMR applications to high-resolution chemical and biological measurements under inhomogeneous magnetic field conditions.

12.
Cell Death Discov ; 10(1): 42, 2024 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-38263152

RESUMEN

The gas therapy is drawing increasing attention in the treatment of many diseases including cancer. As one of gas signaling molecules, carbon monoxide (CO) has been proved to exert anti-cancer effects via triggering multiple cell death types, such as autophagy, apoptosis and necrosis. Here, we showed that low concentration CO delivered from CO-releasing molecule 3 (CORM-3) effectively induced ferroptosis, known as a novel proinflammatory programmed cell death, in vitro and in vivo. Mechanistically, we found that CO triggered ferroptosis by modulating the ROS/GSK3ß/GPX4 signaling pathway, resulting in the accumulation of lipid hydroperoxides and the occurrence of ferroptosis. We think our findings provide novel insights into the anti-cancer mechanisms of CO, and suggest that CO could potentially be exploited as a novel ferroptosis inducer for cancer treatment in the future.

13.
Cell Death Dis ; 14(8): 543, 2023 08 23.
Artículo en Inglés | MEDLINE | ID: mdl-37612280

RESUMEN

Haploinsufficient mutation in arginine and glutamine-rich protein 1 (Arglu1), a newly identified pre-mRNA splicing regulator, may be linked to neural developmental disorders associated with mental retardation and epilepsy in human patients, but the underlying causes remain elusive. Here we show that ablation of Arglu1 promotes radial glial cell (RG) detachment from the ventricular zone (VZ), leading to ectopic localized RGs in the mouse embryonic cortex. Although they remain proliferative, ectopic progenitors, as well as progenitors in the VZ, exhibit prolonged mitosis, p53 upregulation and cell apoptosis, leading to reduced neuron production, neuronal loss and microcephaly. RNA seq analysis reveals widespread changes in alternative splicing in the mutant mouse embryonic cortex, preferentially affecting genes involved in neuronal functions. Mdm2 and Mdm4 are found to be alternatively spliced at the exon 3 and exon 5 respectively, leading to absence of the p53-binding domain and nonsense-mediated mRNA decay (NMD) and thus relieve inhibition of p53. Removal of p53 largely rescues the microcephaly caused by deletion of Arglu1. Our findings provide mechanistic insights into cortical malformations of human patients with Arglu1 haploinsufficient mutation.


Asunto(s)
Empalme Alternativo , Microcefalia , Humanos , Animales , Ratones , Empalme Alternativo/genética , Microcefalia/genética , Proteína p53 Supresora de Tumor/genética , Empalme del ARN , Apoptosis/genética , Péptidos y Proteínas de Señalización Intracelular
14.
Front Immunol ; 14: 1153423, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37006285

RESUMEN

Background: Hepatocellular carcinoma (HCC) is a complex disease with a poor outlook for patients in advanced stages. Immune cells play an important role in the progression of HCC. The metabolism of sphingolipids functions in both tumor growth and immune infiltration. However, little research has focused on using sphingolipid factors to predict HCC prognosis. This study aimed to identify the key sphingolipids genes (SPGs) in HCC and develop a reliable prognostic model based on these genes. Methods: The TCGA, GEO, and ICGC datasets were grouped using SPGs obtained from the InnateDB portal. A prognostic gene signature was created by applying LASSO-Cox analysis and evaluating it with Cox regression. The validity of the signature was verified using ICGC and GEO datasets. The tumor microenvironment (TME) was examined using ESTIMATE and CIBERSORT, and potential therapeutic targets were identified through machine learning. Single-cell sequencing was used to examine the distribution of signature genes in cells within the TME. Cell viability and migration were tested to confirm the role of the key SPGs. Results: We identified 28 SPGs that have an impact on survival. Using clinicopathological features and 6 genes, we developed a nomogram for HCC. The high- and low-risk groups were found to have distinct immune characteristics and response to drugs. Unlike CD8 T cells, M0 and M2 macrophages were found to be highly infiltrated in the TME of the high-risk subgroup. High levels of SPGs were found to be a good indicator of response to immunotherapy. In cell function experiments, SMPD2 and CSTA were found to enhance survival and migration of Huh7 cells, while silencing these genes increased the sensitivity of Huh7 cells to lapatinib. Conclusion: The study presents a six-gene signature and a nomogram that can aid clinicians in choosing personalized treatments for HCC patients. Furthermore, it uncovers the connection between sphingolipid-related genes and the immune microenvironment, offering a novel approach for immunotherapy. By focusing on crucial sphingolipid genes like SMPD2 and CSTA, the efficacy of anti-tumor therapy can be increased in HCC cells.


Asunto(s)
Carcinoma Hepatocelular , Neoplasias Hepáticas , Humanos , Pronóstico , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/terapia , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/terapia , Inmunoterapia , Nomogramas , Microambiente Tumoral/genética
15.
Exp Ther Med ; 23(6): 425, 2022 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-35607373

RESUMEN

In patients with diabetes, the Wnt/ß-catenin pathway in vascular smooth muscle cells (VSMCs) is continuously activated by low-intensity inflammation, which leads to the osteoblastic differentiation of these cells and the deposition of calcium and phosphorus in blood vessels. The aim of the present study was to determine whether long intergenic non-coding RNA-erythroid pro-survival (lincRNA-EPS) was able to ameliorate vascular calcification (VC) associated with diabetes. VSMCs isolated from C57BL/6 mice were transfected with lincRNA-EPS overexpression vector in vitro and their osteoblastic differentiation was evaluated under high-glucose conditions. In addition, a mouse model of diabetes was established, which included a lincRNA-EPS knockout group and a lincRNA-EPS high expression group. Blood vessel samples from the mice were examined to determine the degree of calcification. The levels of inflammatory factors in serum were also detected. The VSMCs transfected with lincRNA-EPS overexpression vector exhibited less osteoblastic differentiation and migration and significantly lower levels of Wnt pathway-associated proteins than those transfected with empty control. Furthermore, the in vivo experiments revealed that the overexpression of lincRNA-EPS significantly reduced VC in diabetic mice. Therefore, on the basis of these findings, it is suggested that lincRNA-EPS overexpression may provide a novel and effective method for the treatment of VC in patients with diabetes.

16.
Methods Appl Fluoresc ; 10(3)2022 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-35483353

RESUMEN

A novel fluorescence sensor for successive detection of Cu2+and Fe3+based on anti-B18H22derivative which possesses 5-hydroxyisoquinoline as an ionophore was synthesized via a one-pot and its structure and photophysical properties were characterized by NMR, HRMS, FTIR, UV-vis, PL and theoretical calculation. The fluorophore displays two emission peaks at 460 nm and 670 nm in THF solution coming from the emission of the locally excited state and intramolecular charge transfer fluorescence, respectively. The complex exhibited obvious aggregation-induced emission enhancement (AIEE) characteristics in THF/H2O solution by increasing the aqueous concentration from 70% to 95%. The AIEE molecules showed a high selectivity towards Cu2+over other metal ions by forming a 2:1 metal-to-ligand complex in THF/H2O (fw = 20%) solution, the fluorescence intensity increased as a linear function of the Cu2+concentration at 460 nm due to the inhibition of PET effect. The fluorescent emission was quenched linearly by the addition of Fe3+, which provides a method for successive determination of Cu2+and Fe3+based on 'off-on-off' fluorescence of the fluorescent. The detection limit of Cu2+and Fe3+was 5.7 × 10-6M and 7.2 × 10-5M respectively. Morever, a rapid identification of Cu2+in the aqueous solution by naked eyes can be realized. In addition, the molecules were pH-sensitive, the fluorescence quenching can be observed in strongly alkaline environment. The method has been applied to the determination of copper ions in water samples with satisfactory results.


Asunto(s)
Cobre , Colorantes Fluorescentes , Colorantes Fluorescentes/química , Iones , Espectrometría de Fluorescencia , Agua
17.
Nanomaterials (Basel) ; 10(7)2020 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-32707727

RESUMEN

A broadband terahertz (THz) absorber, based on a graphene metasurface, which consists of a layer of ring-porous patterned structure array and a metallic mirror separated by an ultrathin SiO2 dielectric layer, is proposed and studied by numerical simulation. The simulated results show that the absorptivity of the absorber reaches 90% in the range of 0.91-1.86 THz, and the normalized bandwidth of the absorptivity is 68.6% under normal incidence. In the simulation, the effects of the geometric parameters of the structure on the absorption band have been investigated. The results show that the absorber is insensitive to the incident polarization angle for both transverse electric (TE) and transverse magnetic (TM) under normal incidence. In addition, the absorber is not sensitive to oblique incidence of the light source under TE polarization conditions, and has an approximately stable absorption bandwidth at the incident angle from 0° to 50°. The absorption band can be adjusted by changing the bias voltage of the graphene Fermi level without varying the nanostructure. Furthermore, we propose that a two-layer graphene structure with the same geometric parameters is separated by a dielectric layer of appropriate thickness. The simulated results show that the absorptivity of the two-layer absorber reaches 90% in the range of 0.83-2.04 THz and the normalized bandwidth of the absorptivity is 84.3% under normal incidence. Because of its excellent characteristics based on graphene metamaterial absorbers, it has an important application value in the field of subwavelength photonic devices.

18.
J Magn Reson ; 316: 106757, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32535401

RESUMEN

The tautomeric structure and chemistry of the histidine imidazole ring play active roles in many structurally and functionally important proteins and polypeptides. While in NMR spectroscopy histidine chemical shifts (e.g. 15N, 13C, and 1H) have been commonly used to characterize the tautomeric structure, hydrogen bonding, and torsion angles, homonuclear 15N scalar couplings in histidine have rarely been reported. Here, we propose double spin-echo sequences to compare the observed signals with and without a 90° pulse between the two spin-echo periods, such that their signal ratio as a function of the echo time solely depends on homonuclear scalar couplings, allowing for measuring weak homonuclear scalar couplings without influence from transverse dephasing effects, thus capable of revealing hydrogen-bond mediated 15N-15N J-couplings that can provide direct and definitive evidence for the formation of N…H…N hydrogen-bonding associated with the imidazole ring. We used two 13C,15N labeled histidine samples recrystallized from solutions at pH 6.3 and pH 11.0 to demonstrate the feasibility of this method and reveal the existence of a weak two-bond scalar coupling between the Nδ1 and Nε2 sites in the histidine imidazole ring in three tautomeric states and the presence of a hydrogen-bond mediated scalar coupling between the Nδ1 site in the imidazole ring and the backbone Nα site in the histidine neutral τ and π states. Our results demonstrate that weak 15N homonuclear scalar couplings can be measured even when their values are less than their corresponding intrinsic natural linewidths, thus providing direct and definitive evidence for the formation of N…H…N hydrogen bonding that is associated with the histidine imidazole ring.


Asunto(s)
Histidina/química , Resonancia Magnética Nuclear Biomolecular/métodos , Isótopos de Carbono , Enlace de Hidrógeno , Estructura Molecular , Isótopos de Nitrógeno
19.
Rev Sci Instrum ; 91(1): 015006, 2020 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-32012606

RESUMEN

A Mach-Zehnder interferometer for measurement of temperature is proposed and experimentally demonstrated, which consists of two sections of single mode fiber (SMF) and a section of thin core fiber spliced between the two SMFs. The two welding areas are heated and stretched to improve the split and recombination of light. The wavelength of the resonant dip will shift when temperature varies due to the thermo-optic and thermal expansion effect. The experimental results show that a temperature sensitivity of 65 pm/°C with a linear correlation coefficient of 0.996 can be achieved in a temperature range from 25 °C to 80 °C. Due to its ease of manufacture, low cost, and high sensitivity, the fiber optic temperature sensor is suitable for temperature measurement applications.

20.
J Magn Reson ; 300: 51-60, 2019 03.
Artículo en Inglés | MEDLINE | ID: mdl-30711783

RESUMEN

Magnetic resonance spectroscopy (MRS) provides a noninvasive tool for metabolite characterization of in vivo biological samples. Conventional MRS measurements on biological samples generally suffer from field inhomogeneity caused by intrinsic magnetic susceptibility variations inside samples. Compared to one-dimensional MRS, two-dimensional (2D) J-resolved spectroscopy enables resolving J couplings along one of the spectral dimension and benefits to metabolite identification and analyses. Intermolecular double-quantum coherences (iDQC) has been proven to be insensitive to magnetic field inhomogeneity, herein we propose a MRS approach based on iDQC evolution and optimal echo sampling scheme to achieve high-resolution 2D J-resolved measurements on biological samples. The applicability of the proposed method is evaluated with experiments on an ex vivo pig brain tissue and an in vivo rat brain tissue. Compared to conventional MRS method which is sensitive to field inhomogeneity inside investigated biological tissues, the proposed method holds immunity to this field inhomogeneity and the quality of resulting spectra may not be influenced by localized voxel size variation. The signal to noise ratio enhancement of the proposed method benefitting from the optimal echo signal sampling is verified with a solution experiment. The new method provides a promising way for high-resolution MRS measurements on biological samples. In combination with fast acquisition strategy, it may find some promising biomedical applications.


Asunto(s)
Resonancia Magnética Nuclear Biomolecular/métodos , Algoritmos , Animales , Química Encefálica , Procesamiento de Imagen Asistido por Computador , Campos Magnéticos , Ratas , Ratas Sprague-Dawley , Relación Señal-Ruido , Soluciones , Porcinos
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