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Biomedical subjects

Z Jia

Publications and source records attributed to Z Jia.

At least 145 records · Page 8Linked to original sources
PubMed1995

Crystallization and preliminary X-ray structure solution of Rhizomucor miehei aspartic proteinase.

Rhizomucor miehei aspartic proteinase (M(r) = 38701, 361 residues) has been crystallized in a form suitable for analysis by X-ray diffraction. The flattened rod-shaped crystals were grown from polyethylene glycol 8000 using vapour-diffusion methods. The crystal form is in space group P2(1)2()12(1) [a = 41.67 (2), b = 51.21 (3) and c = 173.3 (2) A], with Z = 4 and one molecule in the asymmetric unit. Data were collected over the range 0 < h < 14, 0 < k < 16 and 0 < l < 62, resulting in 7032 unique reflections to give 72.1% completeness with a merging R of 0.067 to a resolution limit of 2.8 A. A molecular-replacement solution of the structure has been obtained using the aspartic proteinase from Rhizomucor pusillus as a model. Rigid-body refinement of the model and subsequent refinement using molecular dynamics were performed with X-PLOR, leading to a current R-factor of 20.1% for 2.8 A data.

Journal Article↗
PubMed1995

Crystallization and preliminary X-ray crystallographic studies on Type III antifreeze protein.

Type III antifreeze protein, more specifically the recombinant QAE-Sephadex-binding isoform, has been crystallized in 50-55% saturated ammonium sulfate, 0.1 M sodium acetate, pH 4.0-4.5. The resultant crystals belong to the orthorhombic space group P212121 with a = 32.60 A, b = 39.00 A, and c = 46.57 A and diffract to at least 1.7 A. A set of 1.7-A native data has been collected, with completeness 93.4% and Rsym of 0.069. Initial screening for heavy-atom derivatives has yielded a Pt-bound derivative.

Animals↗
PubMed1995

Triterpenoid saponins from Clinopodium chinensis.

Two new triterpenoid saponins, 3 beta,16 beta,23-trihydroxy-13,28-epoxyolean- 11-en-3-yl-[beta-D-glucopyranosyl(1-->4)-beta-D-glucopyranosyl(1-->3)]- [beta-D-glucopyranosyl(1-->2)]-beta-D-fucopyranoside[1](clinopodiside B) and 28-O-beta-D-glucopyranosyl-3 beta,23-dihydroxyoleana-12,21-dien-3-yl-beta-D-glucopyranosy l-(1-->3)-beta-D- fucopyranoside [3] (clinopodiside C), together with three known saikosaponins, buddlejasaponins IV, IVa, and IVb, have been isolated from the plant, Clinopodium chinensis, and characterized using chemical evidence and spectroscopic methods, in particular 2D nmr spectroscopy.

Carbohydrate Sequence↗
PubMed1995

Oleanane triterpene saponins from the Chinese medicinal herb Clinopodium chinensis.

Four oleanne triterpene saponins, 3beta,16beta, 23-trihydroxy-keton-13beta,28-epoxyolean-9(11)-en-3-yl -[beta-D-glucopranosyl(1-->2)]-[beta-D-glucopyranosyl(1-->3)]-beta -D-fucopyranoside [1] (clinopodiside D), 16beta-propionyl-3beta,23-dihydroxyoleana-11-21-dien-3 -yl-[beta-D-glucopyranosyl(1-->2)]-[beta-D-glucopranosyl(1-->3)]-b eta-D-fucopyranoside [2] (clinipodiside E), 3beta,16beta,21alpha,23,28-pentahydroxy-11-methoxyolean++ +-12-en-3-yl-[beta-D-glucopyranolyl(1-->2)]-[beta-D-glucopyranosyl (1-->3)]-beta-D-fucopyranoside [3] (clinopodiside F), and 3beta,16beta,21beta,23,28-pentahydroxyoleana-11,13(18) -dien-3-yl-[beta-D-glucopyranosyl(1-->2)]-[beta-D-glucopyranosyl(1 -->3)]-beta-D-fucopyranoside [4] (clinopodiside G), were isolated and purified from the plant Clinopodium chinensis. Their structures were elucidated on the basis of interpretation of nmr and ms data and from chemical evidence. The results are of potential interest for medicinal reasons.

Carbohydrate Sequence↗
PubMed1995

Triterpenoid saponins from Gypsophila oldhamiana.

Three new triterpenoid saponins were isolated from the roots of Gypsophila oldhamiana. Their structures were elucidated, using a combination of homonuclear and heteronuclear 2D nmr and fabms, as 3-0-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranolyl-(1-->3)] -beta-D-glucuronopyranosyl quillaic acid methyl ester [1], 3-0-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta- D-glucuronopyranosyl gypsogenin methyl ester [2], and 3-0-beta-D-galactopyranolsyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3) ]-beta-D-glucuronopyranosyl quillaic acid 28-[0-beta-D-fucopyranosyl(1-->4)-beta-D-glucopyranosyl(1-->3)]-alpha-L- rhamnopyranosyl] ester.

Carbohydrate Sequence↗
PubMed1995

Protein tyrosine phosphatases take off.

Protein tyrosine phosphatases (PTPs) are a family of signal transduction enzymes that dephosphorylate phosphotyrosine containing proteins. Structural and kinetic studies provide a molecular understanding of how these enzymes regulate a wide range of intracellular processes.

Amino Acid Sequence↗
PubMed1995

Influence of prepartum protein and energy concentrations for dairy goats during pregnancy and early lactation.

Sixty-three multiparous Alpine does were blocked by pregnancy type (single vs. multiple) on d 90 of pregnancy and assigned to one of nine diets to evaluate the interaction of prepartum protein and energy intake on BW change, kidding, and subsequent production and composition of milk. Treatments were factorial with three percentages of CP (8.5, 11.5, and 14.5% of DM) and three concentrations of metabolizable energy (1.80, 2.16, and 2.53 Mcal/kg of DM). Does were fed for ad libitum intake during pregnancy and switched to a lactation diet (16% CP and 2.35 Mcal of metabolizable energy/kg of DM) after parturition. Milk production and composition were recorded for the first 15 wk of lactation. Prepartum BW gain increased quadratically as protein amount increased but was unaffected by energy. Kidding rate, litter weight, and gestation length were unaffected by protein or energy amounts. Milk production in the subsequent lactation increased quadratically in response to prepartum CP (2.59, 3.26, and 3.07 kg/d for 8.5, 11.5, and 14.5% CP, respectively). Milk production increased linearly in response to prepartum metabolizable energy concentration (2.63, 3.05, and 3.26 kg/d for 1.80, 2.16, and 2.53 Mcal/kg of DM, respectively). Milk fat percentage increased linearly in response to increased prepartum energy. Production of milk fat, protein, SNF, FCM, and SCM were affected quadratically by increased prepartum CP and linearly by prepartum energy, following the pattern for milk production. The present recommendations for prepartum CP and energy appear to be adequate for gestation and subsequent lactation performance of dairy goats.

Animals↗
PubMed1995

Immunoglobulin depositions in peripheral nerves in polymyositis.

An immunocytochemical study was performed in 6 peripheral nerve specimens from 6 cases of polymyositis. The results revealed that depositions of IgG, IgM, IgA and C3 were found in the epineurium, perineurium and the walls of capillaries. These findings demonstrated that depositions of immunoglobulins and the complement-mediated immunoreaction may play an important role in pathogenesis of polymyositis with peripheral nerve involvements.

Adult↗
PubMed1994

Repair of spontaneously deamidated HPr phosphocarrier protein catalyzed by the L-isoaspartate-(D-aspartate) O-methyltransferase.

The non-enzymatic deamidation at residues Asn-12 and Asn-38 of Escherichia coli phosphocarrier protein, HPr, and the repair of the resulting L-isoaspartyl (or beta-aspartyl) derivatives, HPr-1 and HPr-2, by recombinant human S-adenosylmethionine-dependent L-isoaspartate-(D-aspartate) O-methyltransferase (EC 2.1.1.77) were investigated. HPr is a component of the bacterial phosphoenolpyruvate:sugar phosphotransferase system that is involved in the concomitant translocation and phosphorylation of many hexose sugars. The major products of the deamidation reaction, L-isoaspartyl (or beta-aspartyl) residues at positions 12 and 38, were found to be substrates for the L-isoaspartate-(D-aspartate) O-methyltransferase, an enzyme active on a wide variety of peptides and proteins containing these abnormal residues. This enzyme has been shown to catalyze the first step in a process that can convert L-isoaspartyl residues in peptides to normal L-aspartyl residues. The affinity of a recombinant human methyltransferase for HPr-1, a form deamidated at Asn-38, was relatively poor (Km = 3.6 mM), while a greater affinity was found for HPr-2, a form deamidated at both Asn-12 and Asn-38 (Km = 197 microM). When HPr-2 was incubated with S-adenosylmethionine and the methyltransferase, the bulk of the L-isoaspartyl residues at position 12 was converted to L-aspartyl residues. The major-by-product was the D-isoaspartyl form. The conversion of L-isoaspartyl residues at position 38 to L-aspartyl residues was less complete, reflecting the lower affinity of the methyltransferase for this site. The phosphohydrolysis activity of the repaired form was found to be midway between the form containing only L-aspartyl residues at positions 12 and 38 and the deamidated HPr-2 form.

Bacterial Proteins↗
PubMed1994

The 1.6 A structure of histidine-containing phosphotransfer protein HPr from Streptococcus faecalis.

The histidine-containing phosphocarrier protein (HPr) is a central component of the phosphoenolpyruvate: sugar phosphotransferase system (PTS) that transports carbohydrates across the cell membrane of bacteria. The three-dimensional structure of Gram-positive Streptococcus faecalis HPr has been determined using the method of multiple isomorphous replacement. The R factor for all data is 0.156 for S. faecalis HPr at 1.6 A resolution with very good geometry. The overall folding topology of HPr is a classical open-faced beta-sandwich, consisting of four antiparallel beta-strands and three alpha-helices. Remarkable disallowed Ramachandran torsion angles of Ala16 at the active center, revealed by the X-ray structure of S. faecalis HPr, demonstrate a unique example of torsion-angle strain that is likely involved directly in protein function. A brief report concerning the torsion-angle strain has been presented recently. A newly-determined pH 7.0 structure is shown to have the same open conformation of the active center and the same torsion-angle strain at Ala16, suggesting that pH is not responsible for the structural observations. The current structure suggests a role for residues 12 and 51 in HPr's function, since they are involved in the active center through direct and indirect hydrogen-bonding interactions with the imidazole ring of His15. It is found that Ser46, the regulatory site in HPr from Gram-positive bacteria, N-caps the minor alpha-B helix and is also involved in the Asn43-Ser46 beta-turn. This finding, in conjunction with the proposed routes of communication between the regulatory site Ser46 and the active center in S. faecalis HPr, provides new insight into the understanding of how Ser46 might function. The putative involvement of the C-terminal alpha-carboxyl group and the related Gly67-Glu70 reverse beta-turn with respect to the function of HPr are described.

Amino Acid Sequence↗
PubMed1994

Triterpenoid saponins from Ardisia crenata.

Two novel triterpenoid saponins, ardisicrenoside A [3 beta-O-(alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-glucopyranosyl- (1-->4)-[beta-D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)- 13 beta,28-epoxy-16 alpha,30-oleananediol] and ardisicrenoside B [3 beta-O-(beta-D-xylopyranosyl-(1-->2)-[beta-D- glucopyranosyl-(1-->4)-[beta-D-glucopyranosyl-(1-->2)]- alpha-L-arabinopyranosyl)-13 beta,28-epoxy-16 alpha,30-oleananediol] were isolated from the roots of Ardisia crenata. Two known triterpenoid saponins, ardisiacrispins A and B were also isolated from this source. Their structures were determined mainly by 2D NMR (COSY, HOHAHA, HETCOR, HMBC and ROESY) experiments. The aglycones are the new 13 beta,28-epoxy-3 beta,16 alpha,30-oleananetriol for ardisicrenosides A and B.

Carbohydrate Sequence↗
PubMed1994

Steroidal saponins from Smilax menispermoidea and S. lebrunii.

Three new (25S)spirost-5-en-3 beta,17 alpha,27-triol glycosides were isolated from the rhizomes and roots of Smilax menispermoidea and S. lebrunii. Their structures were elucidated by means of spectroscopic and chemical methods. Several known saponins were also isolated and identified.

Carbohydrate Sequence↗
PubMed1994

Triterpenoid saponins from Ardisia crenata and their inhibitory activity on cAMP phosphodiesterase.

Two novel triterpenoid saponins, ardisicrenoside C (1) [3 beta-O-(alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->4)- [beta-D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)-16 alpha, 28-dihydroxy-olean-12-en-30-oic acid 30-O-beta-D-glucopyranosyl ester] and ardisicrenoside D (2) [3 beta-O-(beta-D-xylopyranosyl-(1-->2)- beta-D-glucopyranosyl-(1-->4)-[beta-D-glucopyranosyl-(1-->2)]-alpha-L- arabinopyranosyl)-16 alpha, 28-dihydroxy-olean-12-en-30-oic acid 30-O-beta-D-glucopyranosyl ester] were isolated from the roots of Ardisia crenata. Structure assignments are based on spectroscopic data including 2D-NMR (correlation spectroscopy (COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), heteronuclear correlated spectroscopy (HETCOR), heteronuclear multiple bond correlation (HMBC) and rotating frame NOE spectroscopy (ROESY)) experiments and some chemical reactions. In addition, the isolated saponins along with their prosapogenins and sapogenins have been evaluated for their inhibitory activity on cAMP phosphodiesterase as a primary screening test for new medicinal compounds.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1994

The study on improved cryopreservation technique of the ultrastructure of corneal endothelial cells.

The traditional corneal cryopreservation technique was improved. We carried out an experimental study that rabbit corneas were cryopreserved by using polyvinylpyrolidone (PVP) as cryoprotective agent and dimethylsulfoxide (DMSO) as the control. The endothelia of cryopreserved corneas were evaluated by scanning and transmission electron microscopy and vital staining. The study shows that PVP is an excellent extracellular cryoprotective agent and has the characteristic of low toxicity or not toxicity to corneal endothelia. PVP is able to enhance the cryoprotective action of DMSO when combined with DMSO. The changes of the ultrastructure of endothelial cells are able to reflect the endothelial viability.

Animals↗
PubMed1993

The 2.0-A resolution structure of Escherichia coli histidine-containing phosphocarrier protein HPr. A redetermination.

The x-ray structure of Escherichia coli HPr has been redetermined at 2.0-A resolution. In contrast to the previous study (El-Kabbani, O. A. L., Waygood, E. B., and Delbaere, L. T. J. (1987) J. Biol. Chem. 262, 12926-12929), the overall structure is, in general, similar to other reported NMR and x-ray HPr structures, although there are some important differences in detail. The overall folding topology of HPr is a classical open-faced beta-sandwich, consisting of four antiparallel beta-strands and three alpha-helices. The least square refinement produced an R index of 0.135 for all measured unique data between 8.0 and 2.0 A resolution. The active center consists of His15 which is hydrogen bonded to a sulfate anion, and Arg17 which has a fully open conformation. This corresponds to the first observed "semi-closed" conformation of the active center of HPr. The Streptococcus faecalis HPr structure (Jia, Z., Vandonselaar, M., Quail, J. W., and Delbaere, L. T. J. (1993) Nature 361, 94-97) has the "open" conformation in which the side chains of His15 and Arg17 are directed as far away from each other as possible. The Bacillus subtilis HPr (Herzberg, O., Reddy, P., Sutrina, S., Saier, M. H., Jr., Reizer, J., and Kapadia, G. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 2499-2503) has the "closed" conformation in which the side chains of His15 and Arg17 are close together with a sulfate anion located in the active center. The open conformation represents the unphosphorylated form of HPr whereas the closed conformation likely resembles the phosphorylated form of HPr. The semi-closed conformation observed in the E. coli HPr structure could represent a structural intermediate on the phosphorylation/dephosphorylation pathway of HPr.

Amino Acid Sequence↗
PubMed1993

Active-centre torsion-angle strain revealed in 1.6 A-resolution structure of histidine-containing phosphocarrier protein.

The histidine-containing phosphocarrier protein (HPr) is a central component of the phosphoenolpyruvate: sugar phosphotransferase system that transports carbohydrates across the cell membrane of bacteria. A typical phosphotransfer sequence is phosphoenolpyruvate-->enzyme I-->HPr-->enzyme II/IIIsugar-->sugar. This is thermodynamically favourable owing to the participation of the high-energy phosphoenolpyruvate. We report here the structure of HPr from Streptococcus faecalis determined at 1.6 A resolution. Remarkable disallowed Ramachandran torsion angles at the active centre, revealed by the X-ray structure, demonstrate a unique example of torsion-angle strain that is probably directly involved in protein function. During phosphorylation, the active-centre torsion-angle strain should facilitate the phosphotransfer reaction by lowering the activation-energy barrier. A recently reported Bacillus subtilis HPr structure, which represents the phosphorylated state of HPr with no torsion-angle strain, provides direct evidence supporting our hypothesis that torsion-angle strain plays a direct part in the function of HPr. An HPr phosphotransfer cycling mechanism is proposed, based primarily on the structures of HPr and other phosphotransferase system proteins.

Bacterial Proteins↗
PubMed1993

Protection of phenylpropanoid glycosides from Pedicularis against oxidative hemolysis in vitro.

Five phenylpropanoid glycosides from Pedicularis, isoacteoside (1), acteoside (2), echinacoside (3), pedicularioside A (4), cistanoside D (5), and a chemically synthesised compound, permethylacteoside (6), as phenolic compounds can protect against oxidative hemolysis. The inhibitory activity is related to the number of phenolic hydroxy groups. Compounds 1, 2, 3, and 4, possessing four phenolic hydroxy groups, have stronger inhibitory activities than 5 possessing only two phenolic hydroxy groups, and compound 6 with no phenolic hydroxy group inhibited oxidative hemolysis weakly.

Animals↗