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Biomedical subjects

S Nie

Publications and source records attributed to S Nie.

27 records · Page 2Linked to original sources
PubMed1997

Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering

Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10(14) to 10(15), much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.

Journal Article↗
PubMed1997

Optical detection of single molecules.

Recent advances in ultrasensitive instrumentation have allowed for the detection, identification, and dynamic studies of single molecules in the condensed phase. This measurement capability provides a new set of tools for scientists to address important current problems and to explore new frontiers in many scientific disciplines, such as chemistry, molecular biology, molecular medicine, and nanostructured materials. This review focuses on the methodologies and biological applications of single-molecule detection based on laser-induced fluorescence.

DNA↗
PubMed1996

[Effects of processing on specific toxicity and pharmacodynamics of radix Kansui, radix Achyranthis bidentatae and semen Armeniacae amarum].

The comparative toxicological researches on crude and processed drugs show that the activating action of Radix Kansui, Radix Achyranthis Bidentatae and Semen Armeniacae Amarum on EBV-EA can be decreased by processing. Processing can also decrease stimulating activity on mouse skin, inhibit tumor-promoting activity in two stage skin tumor promoting test and lapactic effect by Radix Kansui. Meanwhile the pharmacological effects of these drugs can be retained or increased by processing.

Animals↗
PubMed1996

[Interaction of sugar with phospholipid bilayer--study on the stabilization of liposomes].

Sugars have the capacity to stabilize structure and function of lipid bilayer. In the presence of sugars, liposomes could remain in their intact biological structure and retain as much as 100% of their original contents after drying-rehydration circle. In this review we present molecular mechanism of preserving effect of sugars on lipid bilayer: preventing membrane fusion, affecting the main transition temperature, preventing lateral phase separation and phase transition of L alpha to H(I). This paper also describes the prospect of the application of these studies.

Carbohydrates↗
PubMed1995

[Effect of processing on specific toxicity of radix Achyranthis bidentatae].

To activate Epstein-barr virus in Raji cells in vitro the lowest activation concentrations of ether extracts from Radix Achyranthis Bidentatae unprepared (I), stir-baked with wine (II) and stir-baked with salt (III) required were 0.8.20 and 0.16 micrograms/ml respectively. 5 microliters (equal to 250 mg herb weight)/ear of these extracts had inflammatory effect on mouse ear skin in 4 hours. Ethanol extract of I at concentration 0.04-125 mg/ml did not increase the chromosomal aberration rates in CHL cells. The decoctions of I, II, and III given orally at 15 g/kg x 3d showed no effect on micronucleus rates in mouse bone marrow. Ethanol extracts of I, II, and III at 10 g/kg x 10d did not show any evident antifertility action.

Animals↗
PubMed1994

Probing individual molecules with confocal fluorescence microscopy.

Confocal fluorescence microscopy coupled with a diffraction-limited laser beam and a high-efficiency detection system has been used to study the diffusive movement and emission process of individual fluorescent molecules in the liquid phase at room temperature. The high detection sensitivity achieved at fast data acquisition speeds (greater than 1 kilohertz) allows real-time observation of single-molecule fluorescence without statistical analysis. The results show fluorescence-cycle saturation at the single-molecule level and multiple recrossings of a single molecule into and out of the probe volume as well as the triplet state.

Fluorescein↗
PubMed1994

Raman spectroscopy of human vitreous in proliferative diabetic retinopathy.

PURPOSE: Recent studies have demonstrated increased nonenzymatic glycation in vitreous from patients with diabetic retinopathy. The present study reports the use of Raman spectroscopy as a novel approach for investigating these molecular changes in human vitreous and experimental tissues. METHODS: Near-infrared laser-excited Fourier-transform (FT) Raman spectroscopy (RS) was performed on vitreous specimens obtained at surgery from seven patients with proliferative diabetic retinopathy and from 10 controls. Measurements were also obtained from samples of control and glycated (in vitro) rat tail tendon collagen and demineralized chick bone collagen. RESULTS: Spectroscopy of vitreous samples from patients with diabetic retinopathy revealed two prominent peaks at 1604 cm-1 and 3057 cm-1, corresponding to aromatic C = C and C-H stretching vibrations in pi-conjugated and aromatic molecules. The peak at 1604 cm-1 was threefold higher in vitreous from patients with diabetes than from controls. Spectra obtained from experimental tissues provided evidence suggesting that the results obtained in human vitreous may be due to nonenzymatic glycation and not to the lysyl oxidase pathway. CONCLUSIONS: These findings suggest that human vitreous obtained from subjects with diabetes may be distinguished from control vitreous by FT-RS and that the peaks characterizing the diabetic samples are possibly due to nonenzymatic glycation. Raman spectroscopy may provide a useful method to elucidate the molecular events underlying these abnormalities.

Aged↗