Biomedical subjects

Hongfeng Yin

Publications and source records attributed to Hongfeng Yin.

7 recordsLinked to original sources

PubMed2006

Cyclic esters and cyclodepsipeptides derived from lactide and 2,5-morpholinediones.

The reaction between Bu(n)Li in benzene and the solid polystyrene support PS-C6H4CH2NH2 leads to a lithiated species that can be represented as PS-C6H4CH2NHLi(LiBu)x, where x approximately 4, which is active in the ring-opening of the cyclic esters L-lactide, rac-lactide, and 2,5-morpholinediones. With approximately 10 eq of these monomeric six-membered rings and with heating, cyclic esters (MeCHC(O)O)n and [MeCHC(O)OCHRC(NH)O]n are reversibly released to the solution. These have been characterized by electrospray ionization MS, and some small rings have been separated by gel-permeation chromatography. Addition of NaBPh4 to a heated benzene solution containing these rings preferentially removes the 18-membered rings from solution. For lactide this is shown to form the basis for chemical amplification from a dynamic combinatorial library and lactide can be converted to (MeCHC(O)O)6 in >80% yield. Metallated supports derived from Me2Mg and Et2Zn are less reactive but do show some ability for lactide ring-enlarging. The 18-membered ring (R,R,R,S,S,S)- and meso-(R,S,R,S,R,S)-(MeCHC(O)O)6 and the 24-membered ring (MeCHC(O)OCHPr(i)C(NH)O)4 have been characterized by single-crystal x-ray diffraction studies, together with the complex Na[eta3-S,S,S,S,S,S-(MeCHC(O)O)6]2BPh4.

Journal Article↗

PubMed2006

A strategy for annotating the human milk glycome.

Oligosaccharides in human milk represent a group of bioactive molecules that have evolved to be an abundant and diverse component of human milk, even though they have no direct nutritive value to the infant. A recent hypothesis proposes that they could be substrates for the development of the intestinal microflora and the mucosal immune system. The inability to determine the exact composition of these oligosaccharides limits research and the ability to understand their biological functions. Oligosaccharides isolated from the lipids and proteins of individual human milk samples were analyzed by a combination of techniques including microchip liquid chromatography mass spectrometry (HPLC-Chip/MS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT ICR MS). Accurate mass measurements obtained using an orthogonal time-of-flight (o-TOF) mass spectrometry provided oligosaccharide composition for approximately 200 individual molecular species. Comparison of HPLC-Chip/MS profiles from five different women revealed variations in milk oligosaccharide compositions. HPLC-Chip/MS profiling provides a method for routinely identifying milk oligosaccharides. Tandem MS in combination with exoglycosidase digestion provides unambiguous differentiation of structural isomers.

Chromatography, High Pressure Liquid↗

PubMed2006

Integrated microfluidic devices with enhanced separation performance: application to phosphoproteome analyses of differentiated cell model systems.

This work reports on the application of a microfluidic device integrating nanoscale LC to nanoelectrospray MS (nano-LC-chip-MS) for the analysis of complex protein digests. Peak profile analyses of more than 700 peptide ions, reproducibly detected across replicate nano-LC-chip-MS runs (n = 5), indicated that the system provided RSD values of 0.24% on retention time, +/- 30 ppm on m/z measurement and +/- 30% variation on intensity over three orders of magnitude. RP adsorbant media with different alkyl chains and particle size packed in both trapping and separation channels were investigated to improve the chromatographic performance of this system. A two-fold improvement in chromatographic peak capacity was achieved using microfluidic devices comprising a 5 mircrom C3 trap with 2.5 microm C18 trap separation channel compared to the traditional 5 microm C18 stationary phase. Enhanced sample selectivity for the identification of phosphopeptides was obtained by combining immobilized metal affinity media prior to peptide separation on the RP microfluidic device. This system was evaluated in the context of differential phosphoproteome analyses to identify changes in signaling events and protein expression of human monocytes following the administration of phorbol ester.

Animals↗

PubMed2005

Arylzinc alkoxides: [ArZnOCHPr(i)2]2 and Ar2Zn3(OCHPr(i)2)4 when Ar = C6H5, p-CF3C6H4, 2,4,6-Me3C6H2, and C6F5.

From the reactions between diarylzinc compounds (Ar2Zn) and the alcohol (Pr(i)2CHOH) in toluene, the compounds [ArZn(OCHPr(i)2)]2 (Ar = C6H5, C6F5, p-CF3C6H4, and 2,4,6-Me3C6H2) have been isolated and shown to exist in equilibra with the trinuclear complexes Ar2Zn3(OCHPr(i)2)4 and Ar2Zn when Ar = C6H5, C6F5, and p-CF3C6H4. The trinuclear complexes have also been prepared from reactions of the Ar2Zn compounds with the alcohol, which reveals that the ease of Zn-C(aryl) bond cleavage is sensitive to the nature of the Ar group: C6H5 > 4-CF3C6H4 > C6F5. The molecular structures of Ar2Zn3(OCHPr(i)2)4 where Ar = p-CF3C6H4 and C6F5 and [ArZn(OCHPr(i)2)]2 where Ar = C6F5, p-CF3C6H4, and 2,4,6-Me3C6H2 are reported based on single-crystal X-ray diffraction studies. The X-ray structure of Zn(p-CF3C6H4)2 is also reported. The reactivity of these new compounds toward the polymerization of propylene oxide (PO) and the copolymerization of PO and CO2 have been investigated along with related reactions involving the partial hydrolysis of the Ar2Zn and R2Zn compounds, where R = t-Bu, n-Bu, and n-Oct. These results are compared with the previous studies employing Et2Zn as an organozinc precursor.

Journal Article↗

PubMed2005

Microfluidic chip for peptide analysis with an integrated HPLC column, sample enrichment column, and nanoelectrospray tip.

Current nano-LC/MS systems require the use of an enrichment column, a separation column, a nanospray tip, and the fittings needed to connect these parts together. In this paper, we present a microfabricated approach to nano-LC, which integrates these components on a single LC chip, eliminating the need for conventional LC connections. The chip was fabricated by laminating polyimide films with laser-ablated channels, ports, and frit structures. The enrichment and separation columns were packed using conventional reversed-phase chromatography particles. A face-seal rotary valve provided a means for switching between sample loading and separation configurations with minimum dead and delay volumes while allowing high-pressure operation. The LC chip and valve assembly were mounted within a custom electrospray source on an ion-trap mass spectrometer. The overall system performance was demonstrated through reversed-phase gradient separations of tryptic protein digests at flow rates between 100 and 400 nL/min. Microfluidic integration of the nano-LC components enabled separations with subfemtomole detection sensitivity, minimal carryover, and robust and stable electrospray throughout the LC solvent gradient.

Chromatography, High Pressure Liquid↗

PubMed2005

Nanoliquid chromatography-mass spectrometry of oligosaccharides employing graphitized carbon chromatography on microchip with a high-accuracy mass analyzer.

The nanoLC separations of oligosaccharides using microchip-based columns are described. Mixtures of alditols from mucins and human milk are separated on graphitized carbon. The nanoLC-MS device showed high mass accuracy for the oligosaccharides ranging between 1 and 6 ppm on routine analyses. The high mass accuracy readily allowed identification of oligosaccharide peaks and the determination of their compositions. High retention time reproducibility was exhibited by the microchip LC. Little variation was observed for standard sample either alone or in a complex heterogeneous mixture. The nanoLC-MS exhibits excellent capabilities in profiling mixtures of oligosaccharides.

Carbon↗

PubMed2004

An experimental study of chromatographic dynamics in open and packed non-cylindrical conduits.

A systematic investigation of the influence of the perimeter shape of open and particle packed fused silica capillaries on chromatographic properties such as resistance to flow and dispersion of solutes propelled through these channels has been conducted. Verifications of these uncommon experiments with existing theoretical treatments are presented and the insights transferred to a novel polymer chip design with integrated facilities for complex separations. A comparison of the chromatographic performance of a real life proteomics sample on this chip with a capillary column of "similar" dimensions is presented.

Chromatography, High Pressure Liquid↗