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991.
Isopestacin,an isobenzofuranone from Pestalotiopsis microspora,possessing antifungal and antioxidant activities 总被引:6,自引:0,他引:6
Strobel G Ford E Worapong J Harper JK Arif AM Grant DM Fung PC Ming Wah Chau R 《Phytochemistry》2002,60(2):179-183
Isopestacin is an isobenzofuranone obtained from the endophytic fungus Pestalotiopsis microspora. While a few other isobenzofuranones are known from natural sources, isopestacin is the only one having a substituted benzene ring attached at the C-3 position of the furanone ring. The compound was isolated from culture broths of the fungus and crystallized and its structure was determined by X-ray crystallography. Both proton and carbon NMR spectral assignments are also reported for isopestacin. This compound possesses antifungal activity and, as measured by electron spin resonance specroscopy, it also behaves as an antioxidant scavenging both superoxide and hydroxy free radicals. 相似文献
992.
Sustained expression of transforming growth factor-beta1 by distraction during distraction osteogenesis 总被引:3,自引:0,他引:3
Distraction osteogenesis is a well-established clinical treatment for limb length discrepancy and skeletal deformities. In our previous studies, we have shown that the tension at the distraction gap correlated with the plasma bone specific alkaline phosphatase activity during distraction. Transforming growth factor-beta1 (TGF-beta1) has been shown to have a regulatory role in alkaline phosphatase activity during fracture healing. This study is to investigate the expression of TGF-beta1 during distraction as a biological response to mechanically stimulated osteoblastic activity by immunohistochemistry. The expression of TGF-beta1 in the distraction callus was compared with that in the fracture callus. During the distraction phase, the osteoblasts and osteocytes expressed a high level of TGF-beta1. Moderate expression of TGF-beta1 was observed in fibroblast-like cells in the fibrous zone of the distraction callus. After the distraction stopped, the expression of TGF-beta1 in different cell types decreased. In fracture healing, the strong expression of TGF-beta1 declined after the first week. Our results showed that the mechanical force induced and sustained TGF-beta1 expression in osteoblasts and fibroblasts-like cells of the distraction callus. Transforming growth factor-beta1 may play a role in transducing mechanical stimulation to biological tissue during in distraction osteogenesis. 相似文献
993.
Lum JH Fung KL Cheung PY Wong MS Lee CH Kwok FS Leung MC Hui PK Lo SC 《Proteomics》2002,2(9):1123-1130
Oriental ginseng (Panax ginseng C. A. Meyer) and American ginseng (Panax quinquefolius) are two widely used valuable traditional Chinese medicines (TCM). Previously, the identification of ginseng was mainly performed by analyzing the ginsengnosides using high performance liquid chromatography and amplification of polymorphic DNA using polymerase chain reaction. However, these methods cannot be used to distinguish TCM samples which are from different parts (main root, lateral roots, rhizome head and skin) of ginseng and ginseng culture cells from wild-grown ginseng. The present study aimed to identify different species of ginseng, different parts of the same ginseng and cultured cells of ginseng using a proteomic approach. Two-dimensional electrophoresis (2-DE) maps were established from the American ginseng main root, different parts (main root, lateral roots, rhizome head and skins) of Oriental ginseng and Oriental ginseng culture cells. Our results show that the 2-DE maps of different ginseng samples contain sufficient differences to permit easy discrimination. We have also identified common and specific protein spots in the 2-DE maps of different ginseng samples. The use of these "marker proteins" may help to speed up the identification process. 相似文献
994.
We have determined the solution NMR structure of a recombinant peptide that consists of the first 156 residues of erythroid alpha-spectrin. The first 20 residues preceding the first helix (helix C') are in a disordered conformation. The subsequent three helices (helices A1, B1, and C1) form a triple helical bundle structural domain that is similar, but not identical, to previously published structures for spectrin from Drosophila and chicken brain. Paramagnetic spin label-induced NMR resonance broadening shows that helix C', the partial domain involved in alpha- and beta-spectrin association, exhibits little interaction with the structural domain. Surprisingly, helix C' is connected to helix A1 of the structural domain by a segment of 7 residues (the junction region) that exhibits a flexible disordered conformation, in contrast to the predicted rigid helical structure. We suggest that the flexibility of this particular junction region may play an important role in modulating the association affinity of alpha- and beta-spectrin at the tetramerization site of different isoforms, such as erythroid spectrin and brain spectrin. These findings may provide insight for explaining various physiological and pathological conditions that are a consequence of varying alpha- and beta-subunit self-association affinities in their formation of the various spectrin tetramers. 相似文献
995.
Herrera C Spenlehauer C Fung MS Burton DR Beddows S Moore JP 《Journal of virology》2003,77(2):1084-1091
We have investigated whether nonneutralizing monoclonal antibodies (MAbs) to the gp120 subunit of the envelope glycoprotein (Env) complex of human immunodeficiency virus type 1 (HIV-1) can interfere with HIV-1 neutralization by another anti-gp120 MAb. We used neutralizing (b12) and nonneutralizing (205-42-15, 204-43-1, 205-46-9) MAbs to the epitope cluster overlapping the CD4-binding site (CD4BS) on gp120. All the MAbs, neutralizing or otherwise, cross-competed for binding to monomeric gp120, indicating the close topological proximity of their epitopes. However, the nonneutralizing CD4BS MAbs did not interfere with the neutralization activity of MAb b12. In contrast, in a binding assay using oligomeric Env expressed on the surface of Env-transfected cells, the nonneutralizing MAbs did partially compete with b12 for Env binding. The surface of Env-transfected cells contains two categories of binding site for CD4BS MAbs. One type of site is recognized by both b12 and nonneutralizing CD4BS MAbs; the other is recognized by only b12. Binding assays for Env-gp120 interactions based on the use of monomeric gp120 or Env-transfected cells do not predict the outcome of HIV-1 neutralization assays, and they should therefore be used only with caution when gauging the properties of anti-Env MAbs. 相似文献
996.
Khan N Shen J Chang TY Chang CC Fung PC Grinberg O Demidenko E Swartz H 《Biochemistry》2003,42(1):23-29
The effect of the cholesterol content of the plasma membrane on the intracellular concentration of oxygen in Chinese hamster ovary (CHO) cells and their mutants was investigated by EPR oximetry. Total and free cholesterol content was significantly higher in 25 RA CHO cells as compared to wild-type and M 19 CHO cells, with most of the free cholesterol in normal and mutant CHO cells located in the plasma membrane. The plasma membrane cholesterol content also was altered by various biochemical means, and the effect on the oxygen gradient was studied. Comparing the three cell lines, the gradient was larger with increased content of cholesterol in the plasma cell membrane. This result also is supported by an additional increase in the oxygen gradients with the incorporation of additional cholesterol in the plasma membrane and a decrease in the oxygen gradient when the cholesterol was depleted from the plasma membrane. The results indicate that the concentration of cholesterol in the plasma membrane can be an important factor for the magnitude of the oxygen gradient observed across the cell membrane. 相似文献
997.
Purine nucleoside phosphorylase had previously been engineered to accept 6-amino substituted purine nucleosides by two active site substitutions, Asn243Asp; Lys244Gln. In the present study, recombinant adenosine phosphorylase (AP) has been conjugated to branched polyethylene glycol (PEG) polymers of approximately 42.5 kDa. Matrix-assisted laser desorption/ionization analysis and SDS acrylamide electrophoresis analysis indicated a subunit composition of greater than 205 kDa consistent with the conjugation of as many as four PEG molecules per AP subunit. The PEG-conjugated enzyme retained greater than 90% of the native catalytic activity. Administration of the enzyme to mice demonstrated the PEG-AP to have a 67-fold increased plasma half-life compared to the native enzyme, 65.1+/-2.9 h versus 57.8+/-1.1 min, respectively. PEG-AP was principally confined to the plasma with minimal activity detected in tissues and of these spleen had the greatest activity and essentially no activity was found in urine. PEG-AP has retained activity with inosine and its injection into PNP-deficient mice resulted in a 2.7-fold increase in urine urate. AP was also shown to protect human CEM cells in culture from the toxic effects of 2'-deoxyadenosine. These studies provide evidence for consideration of PEG-AP as an alternative enzyme therapy for the inherited deficiency of adenosine deaminase. 相似文献
998.
Fung BM 《Biophysical journal》2003,85(6):3429-3430
999.
Current achievements using ProteinChip Array technology 总被引:16,自引:0,他引:16
Because of its inherent flexibility, the ProteinChip Array platform has demonstrated utility into basic research as well as clinical research. In the domain of basic research, it has been used to examine protein modifications, characterize protein-protein interactions and study signal transduction and enzymatic pathways. In clinical research, it has been used to elucidate and identify biomarkers of disease, and as a platform for predictive medicine. 相似文献
1000.
We used cysteine-scanning and spin-labeling methods to prepare singly spin labeled recombinant peptides for electron paramagnetic resonance studies of the partial domain regions at the tetramerization site (N-terminal end of alpha and C-terminal end of beta) of erythroid spectrin. The values of the inverse line width parameter (deltaH0(-1)) from a family of Sp alphaI-1-368delta peptides scanning residues 21-30 exhibited a periodicity of approximately 3.5-4. We used molecular dynamics calculations to show that the asymmetric mobility of this helix is not necessarily due to tertiary contacts, but is likely due to intrinsic properties of helix C', a helix with a heptad pattern sequence. The residues with low deltaH0(-1) values (residues at positions 21, 25, and 28/29) were those on the hydrophobic side of this amphipathic helix. Native gel electrophoresis results showed that these residues were functionally important and are involved in the tetramerization process. Thus, EPR results readily identified functionally important residues in the alpha spectrin partial domain region. Mutations at these positions may lead to clinical symptoms. Similarly, the deltaH0(-1) values from a family of spin-labeled Sp betaI-1898-2083delta peptides also exhibited a periodicity of approximately 3.5-4, indicating a helical conformation in the two scanned regions (residues 2008-2018 and residues 2060-2070). However, the region consisting of residues 2071-2076 was in a disordered conformation. Both helical regions include a hydrophilic side with high deltaH0(-1) values and a hydrophobic side with low deltaH0(-1) values, demonstrating the amphipathic nature of the helical regions. Residues 2008, 2011, 2014, and 2018 in the first scanned region and residues 2061, 2065, and 2068 in the second scanned region were on the hydrophobic side. These residues were critical in alphabeta spectrin association at the tetramerization site. Mutations at some of these positions have been reported to be detrimental in clinical studies. 相似文献