Biomedical subjects

S Sun

Publications and source records attributed to S Sun.

At least 109 records · Page 6Linked to original sources

PubMed2000

[In situ time-resolved FTIR studies of HCOOH oxidation on Pt(100)/Sb electrodes].

The electrocatalytic oxidation of formic acid on Pt(100)/Sb electrodes of different coverage of Sb was investigated by using electrochemical techniques and in situ time-resolve FTIRS. The results demonstrated that the dissociative adsorption of formic acid was inhibited by the presence of Sbad on Pt(100) surface, as a consequence HCOOH can be oxidized directly into CO2 via reactive intermediates. The rate of oxidation of formic acid varied with the coverage of Sbad. It was revealed that at a Sbad coverage of 0.24 the Pt(100)/Sb electrode exhibited the highest electrocatalytic activity for HCOOH oxidation.

English Abstract↗

PubMed2000

[In-situ FTIR spectroscopic studies of electro oxidation of ethanol in alkaline media at a nm-Pt/GC electrode].

The electro-oxidation of ethanol on a nm-Pt/GC electrode in alkaline solutions was investigated by using cyclic Voltammetry and in-situ FTIR spectroscopy. The results demonstrated that the main product of ethanol oxidation was CH3COO-, only small quantity of CH3CHO was determined simultaneously. In contrast with the dual path reaction mechanism for the oxidation of ethanol in acid media, the oxidation of ethanol in alkaline media was revealed via the intermediate process of dissociative adsorption.

English Abstract↗

PubMed2000

[The analysis of linseed oil by FTIR and FT-Raman].

Linseed oil is an important natural sanitarian oil. To qualitative analyses the linseed oil, FTIR and FT-Raman were used to identify the contents of it. It is indicated that each component has characteristic frequency, and can be discriminated from others by IR and Raman spectroscopy. This is useful for the further on-line quantitative analysis and quality control of linseed oil.

Fourier Analysis↗

PubMed2000

[Study on thermal unfolding process of trichosanthin by FTIR spectroscopy].

Fourier-transform infared spectroscopy, combined with resolution-enhancement techniques including second-derivative spectroscopy, Fourier self-deconvolution and curvefitting technique, was used to investigate the thermally induced unfolding process of anti-HIV-I toxin protein trichosanthin. During heating from 25 degrees C to 85 degrees C, the peak of Amide I shifted to 1618 cm-1 while the secondary structural contents change with the temperature. Upon cooling the protein from 85 degrees C to 25 degrees C, the contour of the Amide I do not change. All these show that the thermal unfolding of trichosanthin is an irreversible intermolecular aggregation process between 25 degrees C and 85 degrees C. The changes of secondary structures with temperature suggest the presence of folding intermediates.

Hot Temperature↗

PubMed2000

[Quantitative analysis of rutin and vitamin C by NIR FTIR].

In this paper, near-infrared diffuse reflectance spectroscopy(NIRDRS) method was used as a quantitative tool to measure the solid mixture of rutin and vitamin C by collecting NIR spectra in the range 7,000-3,900 cm-1. The quantitative mathematics model was established with partial least squares(PLS) method. The correlation coefficient was 99.75%, the standard error of Rutin was 0.363%, and the standard error of Vitamin C was 1.078%. The methods are rapid, exact and nondestructive to samples. The components of the samples can be individually analyzed with high accuracy and precision, so NIRDRS can be a useful method of quality control of pharmaceuticals in the future.

Ascorbic Acid↗

PubMed2000

[Study on unfolding process of neo-trichosanthin in the presence of GdnHCl].

Fluorescence spectroscopy and circular dichroism are effective instruments to determine the chemical unfolding process of protein solution. In this paper, both of them were selected to investigate the unfolding processes of neo-trichosanthin in the presence of GdnHCl. One GdnHCl is added, both spectra of fluorescence and circular dichroism changed remarkedly. The denaturation curve of CD ellipticity meets that of fluorescence intensive excitation at 295 nm very well. The result shows that, in the presence of GdnHCl, the unfolding of neo-trichosantin matches the two-state process well. The model is different from the model of trichosanthin that others reported previously. The mechanism will be further probed later.

Circular Dichroism↗

PubMed2000

[In situ FTIR spectrocopic studies of CO and CN- adsorbed on electrode of nanometer thin film of palladium in alkaline solutions].

The adsorption and coadsorption of CO and CN- on electrode of nanometer thin film of palladium (nm-Pd/GC) was studied by using in situ FTIR spectroscopy. The results demonstrated that the nm-Pd/GC electrode exhibited abnormal infrared effects (AIREs) in alkaline solutions as in acid solutions. The characters of AIREs, i.e., the inversion of the direction of IR band, the augmentation of FWHM and the significant enhancement of IR absorption by adsorbed species were observed in all cases of adsorption and coadsorption of CO and CN-. It has been illustrated that strong interaction is existed between adsorbed CO and CN- on nm-Pd/GC surface. The study has contributed towards understanding the surface processes of chemisorption as well as to reveal the origin of nanometer size-effects of thin film materials.

English Abstract↗

PubMed2000

[In situ FTIRS studies of CO2 reduction on thin film alloy electrodes].

The nanometer thin film alloy electrode (Sb-Pb-Pt/GC) was prepared by electrochemical methods. Excellent catalytic effect was observed on these film alloy material in the electro-reduction of carbon dioxide (CO2). The reduction can take place at potentials as high as -0.4 V. The oxidation of reduced products of CO2 on Sb-Pb-Pt/GC yielded current peaks at arrowed -0.08, 0.2 and 0.3 V, while the oxidation of reduction products on a nm-Pt/GC electrode gave rise a current peak near 0.4 V. The in situ FTIR spectroscopic studies confirmed at a molecule level that the products of CO2 reduction on Sb-Pb-Pt/GC are mainly organic acid and alcoholic compounds, while on a nm-Pt/GC electrode the production of CO2 is mainly CO species.

Alloys↗

PubMed2000

[In situ FTIR spectrocopic investigations of 1,3-butanediol oxidation on Sb and S modified Pt electrodes].

In the present paper, we studied the surface structure effect of Pt electrode modified with antimony and sulfur adatoms towards 1,3-Butanediol oxidation. The results demonstrated that the modification of Sb and S both inhibited the dissociative adsorption of 1,3-Butanediol into CO, which is the main source of self-poisoning in electrocatalysis of small organic molecules. At lower potentials, the principal oxidation pathway of 1,3-Butanediol on Pt/Sbad electrode is towards the production of C=O. However, at higher potentials, the products of CO2 increased. The presence of S(ad) inhibited the oxidation of 1,3-BD at low potentials(< 0.8 V), and yield mainly acid species as products at higher potentials(> 0.8 V).

Antimony↗

PubMed2000

[In situ FTIR studies of CO adsorption on palladium loading zeolite electrode].

Adsorption of CO on palladium loading zeolite electrode supported on Pt or GC substrate was studied by in situ MSFTIR spectroscopy. The results demonstrated that the geometry of faujasite supercages favors the formation of bridge-bonded CO species. The enhanced IR adsorption of CO adsorbed on Pd clusters located in the supercages of zeolite has been observed for the first time, which is a new phenomenon and differs from the abnormal infrared effects discovered by our group and the surface enhanced infrared absorption phenomenon reported in the literature.

English Abstract↗

PubMed2000

[In situ FTIRS studies of reduction of [OsVI(N)(NH3)4](CF3SO3)3 in acetonitrile].

In this paper, the electrochemical cyclic voltammetry, UV/Vis and in situ FTIR spectroscopy were used to study the electrochemical reduction of [OsVI(N)(NH3)4](CF3SO3)3 on GC and Pt electrode in acetonitrile. The results demonstrated that the N-N coupling can occur between [OsVI(N)(NH3)4]3+ and the osmium(V) species generated at the electrode. It has revealed for the first time, by in situ FTIR spectroscopy, that the IR absorption of the nu (N identical to N) mode of the mu-dinitrogen osmium[III, II] and [II, II] complex yields positive-going band at around 2,019 cm-1 and negative-going band near 1,970 cm-1, respectively. The results provided new insights in understanding the mechanism of the coupling reaction [OsV identical to N][OsVI identical to N]<=>[OsII-N identical to N-OsIII].

English Abstract↗

PubMed2000

[Study on mechanism of different PHAs during heating by FTIR].

In this paper, PHB, P(HO-co-HD), a various composition of P(HB-co-HV) copolymer and P(HB-co-HH) copolymer were studied both at normal temperature and in the process of increasing and decreasing temperature using FTIR spectroscopy technology. Results showed that FTIR spectra of PHAs with various compositions have distinguishing characteristics. Physical transformation occurred when PHAs were treated with heat denaturalization, and this physical process was reversible.

Bacteria↗

PubMed2000

[Spectral analysis and composition determination of blue ballpoint writing inks].

Main compositions of ballpoint inks were determined by analyzing some tropical Fourier Transform Infrared(FTIR) spectra of 108 kinds of ballpoint inks. By using this method, the blue ink samples have been divided to two groups, 18 species depend on their spectral characteristics such as peak location, peak intensity. The reaction mechanism of age changes due to aging of the ink's compositions was discussed. The study is the first step for establishing the analytical date base of ballpoint inks system and estimating the age of ballpoint in written text has been offered. The advantage of this method is fast, reliable and nondestructive.

Handwriting↗

PubMed2000

[Real time monitor of rutin stability during heating by Fourier transform infrared spectroscopy].

The thermal stability of the natural product of rutin was studied by Fourier Transform Infrared Spectroscopy (FTIR) in this paper for the first time. To monitor the changing of rutin in real time, the temperature-control accessory was also used to in-situ follow the thermal behavior. It is demonstrated that as the temperature increased from 25 degrees C to 270 degrees C, the thermally-induced denaturation of rutin was accompanied by the oxidation and thermal discomposed procedure. The structure of rutin changed at a lower temperature (75 degrees C). This is not only indicating the existence of an intermediate state, but also approved that the stability of rutin is poor. While at the higher temperature (270 degrees C), rutin discomposed into two results. It is proved that this method is fast, accurate and having no solvent effect. Samples can thus be examined undestroyed.

Computer Systems↗

PubMed2000

[The latest development of the research on Chinese medicine by molecular vibrational spectroscopy].

The latest development of the molecular vibrational spectroscopy (Fourier Transform Raman Spectroscopy and Fourier Transform Infraed Spectroscopy) and the latest application of the non-destructive identification, quantitative analysis, thermal-stability monitoring and Chinese medicine optimizing were described in this paper. Some Chinese crude herbs can be directly and quickly identified by Fourier Transform Raman spectroscopy (FT - Raman) and Diffused Reflection Fourier Transform Infrared Spectroscopy (DR-FTIR). The content of Chinese herbs, medicine and medicament can be quantified without destruction by Diffused Reflection Fourier Transform and Near Infrared Spectroscopy (DR-NIR-FTIR). The mechanism of interaction between the Chinese medicine and some cells or bacteria can be in situ monitored by FT-Raman and HATR-FTIR. Best medicine could be selected and medicament could be optimized according to the injury degree of the cell or bacteria. The decomposing and degenerating process of medicines can also be timely monitored by FT-Raman and the temperature controlled FTIR. These are the latest use of molecular spectroscopy in Chinese medicine. The fast indentification, quantitative analysis monitoring, thermal stability predicting and the optimizing of Chinese herbs, medicine and medicament can be guided by the above mentioned methods. It is proved that these methods are nondestructive to samples, fast accurate, and easy to use.

Drug Stability↗

PubMed2000

[Spectrum analysis of blue ball-point ink components by FTIR microsope].

The FT-IR microscope spectra of 108 kinds of blue ball-point writing inks have been analyzed in detail in this paper. According to the transmittance spectra, the composition in the ink such as the solvent, the pigment and the resin was identified. It is the base to determination of the age of ball-point writing inks nondestructively.

Handwriting↗

PubMed1999

The three-dimensional structure of the Limulus acrosomal process: a dynamic actin bundle.

Limulus sperm contains a dynamic macromolecular structure that rapidly extends a 50 microm process called the true discharge. The core of this structure is a bundle of ordered filaments composed of a complex of actin, scruin and calmodulin. We determined its structure by electron crystallographic reconstruction. The three-dimensional map reveals an actin-scruin helix that is azimuthally modulated by the influence of the interactions of a filament with its neighbors. There are a variety of density connections with neighboring filaments involving scruin. Scruin commonly contacts one neighbor, but we observe up to three interfilament connections involving both domains of the 28 scruin molecules in the unit cell. Our structure indicates that promiscuous scruin-scruin contacts are the major determinants of bundle stability in the true discharge. It also suggests that rearrangements would be permitted, which can facilitate the transition from the coiled to the true discharge form.

Acrosome↗

PubMed1999

Three metal ions at the active site of the Tetrahymena group I ribozyme.

Metal ions are critical for catalysis by many RNA and protein enzymes. To understand how these enzymes use metal ions for catalysis, it is crucial to determine how many metal ions are positioned at the active site. We report here an approach, combining atomic mutagenesis with quantitative determination of metal ion affinities, that allows individual metal ions to be distinguished. Using this approach, we show that at the active site of the Tetrahymena group I ribozyme the previously identified metal ion interactions with three substrate atoms, the 3'-oxygen of the oligonucleotide substrate and the 3'- and 2'-moieties of the guanosine nucleophile, are mediated by three distinct metal ions. This approach provides a general tool for distinguishing active site metal ions and allows the properties and roles of individual metal ions to be probed, even within the sea of metal ions bound to RNA.

Animals↗