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Biomedical subjects

Yu Liu

Publications and source records attributed to Yu Liu.

At least 127 records · Page 7Linked to original sources
PubMed2005

Molecular recognition thermodynamics of bile salts by beta-cyclodextrin dimers: Factors governing the cooperative binding of cyclodextrin dimers.

The complex stability constants (K(S)), standard molar enthalpy (DeltaH degrees), and entropy changes (DeltaS degrees) for the inclusion complexation of two families of beta-cyclodextrin (beta-CD) dimers, i.e. beta-CD dimers Se1-Se4 bearing 2,2'-diselenobis(benzoyl) tether (Se-dimers) and beta-CD dimers Py1-Py4 bearing 2,2'-bipyridine-4,4'-dicarboxy tether (Py-dimers), with four bile salt guests, i.e. sodium cholate (CA), sodium deoxycholate (DCA), sodium glycocholate (GCA), and sodium taurocholate (TCA), were determined at 25 degrees C in Tris buffer solution (pH 7.4) at 298.15 K by means of isothermal titration microcalorimetry. The thermodynamic parameters obtained, together with the ROESY spectra of interactions between beta-CD dimers and bile salts, consistently suggest that the length, flexibility, and structure of spacers linking the two beta-CD cavities not only determine the binding modes but also significantly alter the molecular selectivity of beta-CD dimers.

Calorimetry↗
PubMed2005

Impact of pharmaceutical dosage forms on the pharmacokinetics of roxithromycin in healthy human volunteers.

OBJECTIVES: The impact of two different pharmaceutical preparations on the pharmacokinetics of roxithromycin was investigated in healthy human volunteers. METHODS: The degradation kinetics and products of roxithromycin were investigated in simulated gastric fluid and simulated intestinal fluid. Two oral dosage forms of roxithromycin were employed: enteric-coated pellets and dispersible tablets. RESULTS: The degradation half-time of roxithromycin in simulated gastric fluid was 0.23 h, and three main degradation products were characterized. In contrast, roxithromycin was stable in simulated intestinal fluid and remained unchanged after a 1.00 h incubation. The roxithromycin enteric-coated pellets exhibited higher bioavailability and a more potent serum antibacterial activity than the dispersible tablets. CONCLUSIONS: The type of oral dosage forms of roxithromycin altered its pharmacokinetics. Whether or not this affects the in vivo antibacterial efficacy requires further study.

Adult↗
PubMed2005

[Expression of MLRQ subunit gene of NADH oxidoreductase and its clinical significance in malignant tumors of digestive system].

OBJECTIVE: To study the differential expression and possible role of MLRQ subunit gene of nicotinamide adenine dinucleotide reduced (NADH) oxidoreductase in malignant tumors of digestive system. METHODS: Specimens of cancerous tissues and matched adjacent normal tissues resected during operation or biopsy: 38 pairs of specimens of esophageal carcinoma, 7 pairs of specimens of cardiac carcinoma, 14 pairs of specimens of gastric carcinoma, 11 pairs of specimens of colon carcinoma, and 7 pairs of specimens of liver carcinoma underwent PCR test and Northern hybridization to detect the differential expression of MLRQ subunit gene of NADH oxidoreductase. RESULTS: (1) Overexpression of MLRQ subunit gene was found in 31 of the 38 pairs of specimens of esophageal carcinoma (81.6%), 4 of the 7 pairs of specimens of cardiac carcinoma (57.1%), 12 of the 14 pairs of specimens of gastric carcinoma (85.7%), 4 of the 7 pairs of specimens of colon carcinoma (65.6%), and 7 of the 11 pairs of specimens of liver cancer (57.1%). No significant difference among different cancers was observed by X(2) test (all P > 0.05). (2) The up-regulation of MLRQ subunit was not correlated with clinic stage, infiltration degree, lymphatic metastasis, and differentiation of tumor (all P > 0.05). CONCLUSION: MLRQ subunit gene is up-regulated in the malignant tumors of digestive system.

Digestive System Neoplasms↗
PubMed2005

A unique tetramer of 4:5 beta-cyclodextrin-ferrocene in the solid state.

A single crystal of a unique 4:5 inclusion complex between beta-cyclodextrin and ferrocene was prepared and the structure was determined by X-ray crystallographic analysis, showing that four of the five ferrocenes were included in the cavities of four beta-cyclodextrins along the axial orientation of the tetramer, while another was co-included between two beta-cyclodextrins from the equatorial orientation.

Combinatorial Chemistry Techniques↗
PubMed2005

Selective binding and inverse fluorescent behavior of magnesium ion by podand possessing plural imidazo[4,5-f]-1,10-phenanthroline groups and its Ru(II) complex.

[structure: see text] Two podands, 4,4'-[(ethylenedioxy)bis(ethyleneoxy)]bis[1-(2-imidazo[4,5-f]-1,10-phenanthroline)benzene] (1) and [Ru(phen)(2)](2)(1)(PF(6))(4) (2) complex, were synthesized from 1,10-phenanthroline. The photophysical behavior and the binding ability of 1 and 2 with some alkali metal and alkaline earth cations were investigated by UV-vis and fluorescence spectrometry and (1)H NMR experiments as well as fluorescence lifetime measurements. The complex stability constants (K(S)) and Gibbs free energy changes (DeltaG degrees ) for the stoichiometric 1:1 complexation of 1 and 2 with the cations were obtained by the fluorimetric titrations. The podands 1 and 2 exhibit different fluorescent behavior in the cations examined, i.e., fluorescence quenching for 1, and fluorescence enhancement for 2. In particular, 1 showed responses specific for Mg(2+), resulting in readily distinguishable by eye.

Journal Article↗
PubMed2005

Lipase-catalyzed resolution of (2R*,3S*)- and (2R*,3R*)-3-methyl-3-phenyl-2-aziridinemethanol at low temperatures and determination of the absolute configurations of the four stereoisomers.

[reaction: see text] Lipase-catalyzed resolution of (2R*,3S*)-3-methyl-3-phenyl-2-aziridinemethanol, (+/-)-2, at low temperatures gave synthetically useful (2R,3S)-2 and its acetate (2S,3R)-2a with (2S)-selectivity (E = 55 at -40 degrees C), while a similar reaction of (2R*,3R*)-3-methyl-3-phenyl-2-aziridinemethanol, (+/-)-3, gave (2S,3S)-3 and its acetate (2R,3R)-3a with (2R)-selectivity (E = 73 at -20 degrees C). Compound (+/-)-2 was prepared conveniently via diastereoselective addition of MeMgBr to tert-butyl 3-phenyl-2H-azirine-2-carboxylate, (+/-)-1a, which was successfully prepared by the Neber reaction of oxime tosylate of tert-butyl benzoyl acetate 7a. The tert-butyl ester was requisite to promote this reaction. For determination of the absolute configuration of (2S,3R)-2a, enantiopure (2S,3R)-2 was independently prepared in three steps involving diastereoselective methylation of 3-phenyl-2H-azirine-2-methanol, (S)-10, with MeMgBr. The absolute configuration of (2S,3S)-3 was determined by X-ray analysis of the corresponding N-(S)-2-(6-methoxy-2-naphthyl)propanoyl derivative (S,S,S)-13.

Aziridines↗
PubMed2005

Efficient fluorescent sensors of oligopeptides by dithiobis(2-benzoylamide)-bridged bis(beta-cyclodextrin)s: structure in solution, binding behavior, and thermodynamic origin.

Two 6,6'-bis(beta-cyclodextrin)s linked by 2,2'-dithiobis[2-(benzoylamino)ethyleneamino] and 2,2'-dithiobis[2-(benzoylamino)diethylenetriamino] bridges (1 and 2) have been synthesized as cooperative multipoint recognition receptor models for non-aromatic oligopeptides. Their structures in solution and inclusion complexation mechanism are comprehensively investigated by means of circular dichroism, 2D NMR spectra and temperature-dependent fluorescence titrations. The results show that the cooperative 'host-linker-guest' binding mode and the extensive desolvation effect jointly contribute to the guest-induced fluorescence enhancement of bis(beta-cyclodextrin)s. Further examinations on the binding behavior of hosts 1-2 with a series of di- and tri-peptides demonstrate that bis(beta-cyclodextrin) 1 can recognize not only the size/shape of oligopeptides but also the dipeptide sequence, giving an exciting residue selectivity up to 37.5 for Gly-Gly-Gly/Glu-Glu pair and a high sequence selectivity up to 5.0 for Gly-Leu/Leu-Gly pair. These fairly good selectivities are discussed from the viewpoint of cooperative binding, multiple recognition and induced-fit interactions between host and guest.

Fluorescent Dyes↗
PubMed2005

Comparative mitochondrial genomics in zygomycetes: bacteria-like RNase P RNAs, mobile elements and a close source of the group I intron invasion in angiosperms.

To generate data for comparative analyses of zygomycete mitochondrial gene expression, we sequenced mtDNAs of three distantly related zygomycetes, Rhizopus oryzae, Mortierella verticillata and Smittium culisetae. They all contain the standard fungal mitochondrial gene set, plus rnpB, the gene encoding the RNA subunit of the mitochondrial RNase P (mtP-RNA) and rps3, encoding ribosomal protein S3 (the latter lacking in R.oryzae). The mtP-RNAs of R.oryzae and of additional zygomycete relatives have the most eubacteria-like RNA structures among fungi. Precise mapping of the 5' and 3' termini of the R.oryzae and M.verticillata mtP-RNAs confirms their expression and processing at the exact sites predicted by secondary structure modeling. The 3' RNA processing of zygomycete mitochondrial mRNAs, SSU-rRNA and mtP-RNA occurs at the C-rich sequence motifs similar to those identified in fission yeast and basidiomycete mtDNAs. The C-rich motifs are included in the mature transcripts, and are likely generated by exonucleolytic trimming of RNA 3' termini. Zygomycete mtDNAs feature a variety of insertion elements: (i) mtDNAs of R.oryzae and M.verticillata were subject to invasions by double hairpin elements; (ii) genes of all three species contain numerous mobile group I introns, including one that is closest to an intron that invaded angiosperm mtDNAs; and (iii) at least one additional case of a mobile element, characterized by a homing endonuclease insertion between partially duplicated genes [Paquin,B., Laforest,M.J., Forget,L., Roewer,I., Wang,Z., Longcore,J. and Lang,B.F. (1997) Curr. Genet., 31, 380-395]. The combined mtDNA-encoded proteins contain insufficient phylogenetic signal to demonstrate monophyly of zygomycetes.

Bacteria↗
PubMed2005

Expression and significance of heat shock protein 70 and glucose-regulated protein 94 in human esophageal carcinoma.

AIM: To investigate the expression and significance of heat shock protein 70 (HSP70) and glucose-regulated protein 94 (grp94) in human esophageal carcinoma and adjacent normal tissues. METHODS: The expression of HSP70 and grp94 in 78 human esophageal cancer and adjacent normal tissues was studied by immunohistochemistry and pathology photograph analysis. RESULTS: Both esophageal cancer and adjacent normal tissues could express HSP70 and grp94. Of the 78 cases of esophageal carcinoma, 95.0%(72/78) showed positive HSP70, mainly stained in nuclei, while grp94 was mainly stained in cell plasma, and the positive rate was 71.8%(56/78). There was a significant difference in the expression of HSP70 and grp94 between esophageal cancer and adjacent normal tissues (P<0.01). Compared with adjacent normal tissues, there was a significant difference between differential types and HSP70 expression (P<0.01). CONCLUSION: HSP70 and grp94 express differently in cell plasma and nuclei. The expression intensity of HSP70 is related to the differentiation of esophageal carcinoma.

Aged↗
PubMed2005

Supramolecular aggregates constructed from gold nanoparticles and l-try-CD polypseudorotaxanes as captors for fullerenes.

A series of cyclodextrin-based polypseudorotaxanes (PPRs) were constructed by threading native beta-cyclodextrin or l-tryptophan-modified beta-cyclodextrin onto the amino-terminated PPG chains of different lengths. Subsequently, these PPRs were further assembled to form netlike supramolecular aggregates through the linkage of gold nanoparticles, and the resulting water-soluble Au-PPR aggregates were comprehensively characterized by FT-IR, UV, NMR, fluorescence spectroscopy, powder X-ray diffraction patterning, TG-DTA, and transmission electron microscopy. The results showed that the size and sedimentation rate of the Au-PPR aggregates were mainly dependent on the lengths of the PPG chains. Significantly, the Au-PPR aggregate 8, involving many l-tryptophan residues, showed not only a satisfactory water solubility but also a good capturing ability for fullerenes in aqueous solution. The 8-fullerene conjugate thus formed exhibited a good DNA cleavage ability under light irradiation.

DNA↗
PubMed2005

Interactions of human replication protein A with single-stranded DNA adducts.

Human RPA (replication protein A), a single-stranded DNA-binding protein, is required for many cellular pathways including DNA repair, recombination and replication. However, the role of RPA in nucleotide excision repair remains elusive. In the present study, we have systematically examined the binding of RPA to a battery of well-defined ssDNA (single-stranded DNA) substrates using fluorescence spectroscopy. These substrates contain adducts of (6-4) photoproducts, N-acetyl-2-aminofluorene-, 1-aminopyrene-, BPDE (benzo[a]pyrene diol epoxide)- and fluorescein that are different in many aspects such as molecular structure and size, DNA disruption mode (e.g. base stacking or non-stacking), as well as chemical properties. Our results showed that RPA has a lower binding affinity for damaged ssDNA than for non-damaged ssDNA and that the affinity of RPA for damaged ssDNA depends on the type of adduct. Interestingly, the bulkier lesions have a greater effect. With a fluorescent base-stacking bulky adduct, (+)-cis-anti-BPDE-dG, we demonstrated that, on binding of RPA, the fluorescence of BPDE-ssDNA was significantly enhanced by up to 8-9-fold. This indicated that the stacking between the BPDE adduct and its neighbouring ssDNA bases had been disrupted and there was a lack of substantial direct contacts between the protein residues and the lesion itself. For RPA interaction with short damaged ssDNA, we propose that, on RPA binding, the modified base of ssDNA is looped out from the surface of the protein, permitting proper contacts of RPA with the remaining unmodified bases.

DNA Adducts↗
PubMed2005

Effects of extended-access self-administration and deprivation on breakpoints maintained by cocaine in rats.

RATIONALE: Animal models that identify the effects of self-administration histories on subsequent patterns, levels of intake, and other aspects of reinforcement will help clarify the controlling variables of human drug use. OBJECTIVE: Identify the effects of extended-access to cocaine and 1 or 7 days of deprivation on cocaine-maintained breakpoints on a progressive ratio (PR) schedule of reinforcement. METHODS: Male, Sprague-Dawley rats were trained to self-administer intravenous cocaine (expt 1: 1.5 mg/kg per infusion; expt 2: 0.75 mg/kg per infusion), and then given various histories of self-administration and deprivation. Breakpoints, the number of infusions self-administered on a PR schedule, were assessed following the deprivation period. RESULTS: Rates of cocaine intake increased when access to cocaine was extended to 6 h/day. From day 1 to day 14, daily intake increased from 92 (+/-2.5) to 101 (+/-2.8) mg/kg in expt 1, and from 55 (+/-4) to 78 (+/-2.2) mg/kg in expt 2. Total intake across this 2-week period was approximately 1260 and 970 mg/kg in expts 1 and 2. Breakpoints were not different following this escalation period. The introduction of a 7-day deprivation period failed to alter breakpoints. CONCLUSIONS: There is dissociation between changes in rate of cocaine intake (or consumption) and breakpoints maintained on a PR schedule. Extended-access to cocaine produced increases in rate of intake without altering breakpoints. Depending on the experimental question, extended-access conditions may prove useful for studying changes in certain aspects of reinforcement, such as consumption, but not others, such as the strength of a drug as a reinforcer.

Animals↗
PubMed2005

Influence of substrate surface loading on the kinetic behaviour of aerobic granules.

In the aerobic granular sludge reactor, the substrate loading is related to the size of the aerobic granules cultivated. This study investigated the influence of substrate surface loading on the growth and substrate-utilization kinetics of aerobic granules. Results showed that microbial surface growth rate and surface biodegradation rate are fairly related to the substrate surface loading by the Monod-type equation. In this study, both the theoretical maximum growth yield and the Pirt maintenance coefficient were determined. It was found that the estimated theoretical maximum growth yield of aerobic granules was as low as 0.2 g biomass g(-1) chemical oxygen demand (COD) and 10-40% of input substrate-COD was consumed through the maintenance metabolism, while experimental results further showed that the unit oxygen uptake by aerobic granules was 0.68 g oxygen g(-1) COD, which was much higher than that reported in activated sludge processes. Based on the growth yield and unit oxygen uptake determined, an oxidative assimilation equation of acetate-fed aerobic granules was derived; and this was confirmed by respirometric tests. In aerobic granular culture, about 74% of the input substrate-carbon was converted to carbon dioxide. The growth yield of aerobic granules was three times lower than that of activated sludge. It is likely that high carbon dioxide production is the main cause of the low growth yield of aerobic granules, indicating a possible energy uncoupling in aerobic granular culture.

Acetates↗
PubMed2005

Assembly behavior of inclusion complexes of beta-cyclodextrin with 4-hydroxyazobenzene and 4-aminoazobenzene.

To further reveal the factors governing the supramolecular assembly of beta-cyclodextrin (beta-CD) inclusion complexes, two aggregates (1 and 2) were prepared from the inclusion complexes of beta-CD with 4-hydroxyazobenzene and 4-aminoazobenzene, respectively, and their binding behavior were investigated by means of X-ray analysis, UV-vis, NMR, and circular dichroism spectra in both solution and the solid state. The obtained results indicated that the beta-CD/4-hydroxyazobenzene complex 1 could form head-to-head dimers (triclinic system, space group P1) in the solid state, which were further self-assembled to a linear supramolecular architecture by the intra- and interdimer hydrogen bond interactions as well as the intradimer pi-pi interactions. However, when the included guest 4-hydroxyazobenzene was switched to a 4-aminoazobenzene, the resultant beta-CD/4-aminoazobenzene complex 2 (monoclinic system, space group P2(1)) could be self-assembled to a wave-type supramolecular aggregate under similar conditions. Furthermore, the combination of crystallographic and spectral investigations jointly revealed the inclusion complexation geometry of beta-CD with 4-hydroxyazobenzene and 4-aminoazobenzene in both solution and the solid state, which demonstrated that the disparity of substituents in the azobenzenes played an important role in the inclusion complexation and molecular assembly, affecting not only the structural features of aggregates but also the binding abilities of azobenzenes with beta-CD.

Journal Article↗
PubMed2005

Ficolin A and ficolin B are expressed in distinct ontogenic patterns and cell types in the mouse.

Ficolins are a group of proteins characterized by the presence of collagen-like and fibrinogen-like domains. Two of three human ficolins, L-ficolin and H-ficolin, are serum lectins that form complexes with mannose-binding lectin-associated serine proteases (MASPs) and play important roles in the lectin complement pathway. The other human ficolin, M-ficolin, is a non-serum-type ficolin that is expressed in monocytes. Little is known about the physiological roles of ficolins. In this study, we delineated the ontogeny and cell types that express ficolins in mice. RT-PCR analysis showed that the expression pattern of ficolin A expression was closely similar to that of Masps, suggesting that these molecules may function in coordination as components of the lectin complement pathway. The cell types that express ficolin A mRNA in both adult liver and spleen were identified as macrophages by in situ hybridization. Ficolin B exhibited a distinct ontogeny pattern that switched from embryonic liver to postnatal bone marrow and spleen. The cells that express ficolin B mRNA were identified as belonging to the myeloid cell lineage by magnetic sorting and by subsequent RT-PCR in bone marrow cells. Thus, the different spatial-temporal expression patterns of ficolins A and B suggest that these molecules play distinct roles in the prenatal and postnatal stages.

Animals↗
PubMed2005

Chiral nanotechnology.

A review of chiral, nanoscale science and technology is presented, with the subject divided into two topics. The first discusses nanotechnology in the service of asymmetric synthesis, chiral separations, and analysis. The second topic concerns broader research in the nanotechnology realm, where molecular chirality plays a role in the properties of materials, including molecular devices, chiral supramolecules, chiral nanotubes, chiral fullerenes, and DNA nanotechnology.

Journal Article↗
PubMed2005

A unified theory for upscaling aerobic granular sludge sequencing batch reactors.

Aerobic granular sludge sequencing batch reactors (SBR) are a promising technology for treating wastewater. Increasing evidence suggests that aerobic granulation in SBRs is driven by selection pressures exerted on microorganisms. Three major selection pressures have been identified as follows: settling time, volume exchange ratio and discharge time. This review demonstrates that these three major selection pressures can all be unified to one, the minimal settling velocity of bio-particles, that determines aerobic granulation in SBRs. The unified selection pressure theory is a useful guide for manipulating and optimizing the formation and characteristics of aerobic granules in SBRs. Furthermore, the unified theory provides a single engineering basis for scale up of aerobic granular sludge SBRs.

Bacteria, Aerobic↗