Bacterial reduction of hexavalent molybdenum to molybdenum blue

A bacterium that was able to tolerate and reduce as high as 50 mM of sodium molybdate to molybdenum blue has been isolated from a metal recycling ground. The isolate was tentatively identified as Serratia sp. strain Dr.Y8 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. ANOVA analysis showed that isolate Dr.Y8 produced significantly higher (P < 0.05) amount of Mo-blue with 3, 5.1 and 11.3 times more molybdenum blue than previously isolated molybdenum reducers such as Serratia marcescens strain Dr.Y6, E. coli K12 and E. cloacae strain 48, respectively. Its molybdate reduction characteristics were studied in this work. Electron donor sources such as sucrose, mannitol, fructose, glucose and starch supported molybdate reduction. The optimum phosphate, pH and temperature that supported molybdate reduction were 5 mM, pH 6.0 and 37°C, respectively. The molybdenum blue produced from cellular reduction exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium, silver, copper and mercury resulted in approximately 61, 57, 80, and 69% inhibition of the molybdenum-reducing activity at 1 mM, respectively. The reduction characteristics of strain Dr.Y8 suggest that it would be useful in future molybdenum bioremediation.     

Perspective Texture Synthesis Based on Improved Energy Optimization

Perspective texture synthesis has great significance in many fields like video editing, scene capturing etc., due to its ability to read and control global feature information. In this paper, we present a novel example-based, specifically energy optimization-based algorithm, to synthesize perspective textures. Energy optimization technique is a pixel-based approach, so it’s time-consuming. We improve it from two aspects with the purpose of achieving faster synthesis and high quality. Firstly, we change this pixel-based technique by replacing the pixel computation with a little patch. Secondly, we present a novel technique to accelerate searching nearest neighborhoods in energy optimization. Using k- means clustering technique to build a search tree to accelerate the search. Hence, we make use of principal component analysis (PCA) technique to reduce dimensions of input vectors. The high quality results prove that our approach is feasible. Besides, our proposed algorithm needs shorter time relative to other similar methods.     

An efficient chemical approach to bispecific antibodies and antibodies of high valency

Irreversible chemical programming of monoclonal aldolase antibody (mAb) 38C2 has been accomplished with β-lactam equipped mono- and bifunctional targeting modules, including a cyclic-RGD peptide linked to either the peptide (d-Lys⁶)-LHRH or another cyclic RGD unit and a small-molecule integrin inhibitor SCS-873 conjugated to (d-Lys⁶)LHRH. We also prepared monofunctional targeting modules containing either cyclic RGD or (d-Lys⁶)-LHRH peptides. Binding of the chemically programmed antibodies to integrin receptors α(v)β(3) and α(v)β(5) and to the luteinizing hormone releasing hormone receptor were evaluated. The bifunctional and bivalent c-RGD/LHRH and SCS-783/LHRH, the monofunctional and tetravalent c-RGD/c-RGD, and the monofunctional bivalent c-RGD chemically programmed antibodies bound specifically to the isolated integrin receptor proteins as well as to integrins expressed on human melanoma M-21 cells. c-RGD/LHRH, SCS-783/LHRH, and LHRH chemically programmed antibodies bound specifically to the LHRH receptors expressed on human ovarian cancer cells. This approach provides an efficient, versatile, and economically viable route to high-valency therapeutic antibodies that target defined combinations of specific receptors. Additionally, this approach should be applicable to chemically programmed vaccines.     

Mechanistic studies on aromatase and related C---C bond cleaving P-450 enzymes

Some P-450 systems, notably aromatase and 14-demethylase catalyse not only the hydroxylate reaction but also the oxidation of an alcohol into a carbonyl compound as well as a C---C bond cleavage process. All these reactions occur at the same active site. A somewhat analogous situation is noted with 17-hydroxylase-17,20-lyase that participates in hydroxylation as well as C---C bond cleavage process. The C---C bond cleavage reactions catalysed by the above enzymes conform to the general equation:

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It is argued that all three types of reaction catalyzed by these enzymes may be viewed as variations on a common theme. In P-450 dependent hydroxylation the initially formed Fe^III---O---O^. species is converted into Fe^III---O---OH and the heterolysis of the oxygen—oxygen bond of the latter then gives the oxo-derivative for which a number of canonical structures are possible; for example Fe^V = O ↔ (+^.)Fe^IV = O ↔ Fe^IV---O^.. One of these, Fe^IV---O^. behaves like an alkoxyl radical and participates in hydrogen abstraction from C---H bond to produce Fe^IV---OH and carbon radical. The latter is then quenched by the delivery of hydroxyl radical from Fe^IV---OH. The latter species may thus be regarded as a carrier of hydroxyl radical. We have proposed that the C---C bond cleavage reaction occurs through the participation of the Fe^III---O---OH species that is trapped by the electrophilic property of the carbonyl compound giving a peroxide adduct that fragments to produce an acyl—carbon cleavage. Scientific developments leading up to this conclusion are considered. In the first author's views,

“The study of mechanisms is not a scientific but a cultural activity. Mechanisms do not aim at an absolute truth but are intended to be a “running” commentary on the status of knowledge in a field. As the structural knowledge in a field advances Mechanisms evolve to take note of the new findings. Just as a constructive “running” commentary provides the stimulus for higher standards of performance, so Mechanisms call for better and firmer structural information from their practitioners”.     

Rat ovarian angiotensin II receptors. Characterization and coupling to estrogen secretion

Angiotensin II receptor agonist (125I-angiotensin II) and antagonist (125I-[Sar1,Ile8]angiotensin II) bind in a specific and saturable manner to rat ovarian membranes. Agonist and antagonist binding affinity (KD approximately 0.5 nM) and the number of sites estimated (Bmax approximately 60 fmol/mg of protein) were similar. Dissociation of receptor-bound agonist was more rapid than the dissociation of receptor-bound antagonist, and agonist, but not antagonist, dissociation from the receptor was accelerated by GTP gamma S. A 0-150 mM increase in Na+ produced a 27% increase in the KD of agonist binding. Antagonist binding was not modified by Na+. These studies suggest that both agonist and antagonist identify putative angiotensin II receptors in the ovary but that the properties of agonist and antagonist binding are distinct. Angiotensin II antagonist binding sites are present on the granulosa cell layer of rat ovarian follicles (Speth, R. C., Bumpus, F. M., and Husain, A. (1986) Eur. J. Pharmacol. 130, 351-352). To determine the role of angiotensin II in ovarian function, we examined angiotensin II receptors and function during the onset of puberty. High affinity and low capacity angiotensin II receptors were present in ovaries from immature rats. After pregnant mare's serum gonadotropin induced ovulation in immature rats, antagonist binding to total ovarian membranes increased over 3-fold. In vitro incubation of peripubertal ovaries with 1 microM angiotensin II produced a stimulation of estrogen, but not progesterone, secretion. This steroidogenic effect of angiotensin II was most pronounced in the luteal phase of the estrus cycle. These studies point toward the involvement of angiotensin II in the regulation of ovarian function, possibly through modulation of follicular estrogen levels.     

Quantitative DNA analysis of low grade cervical intraepithelial neoplasia and human papillomavirus infection by static and flow cytometry.

Quantitative deoxyribonucleic acid (DNA) analysis of cervical biopsy specimens from 26 women with cytological, colposcopic, and histological evidence of mild cervical atypia consistent with cervical intraepithelial neoplasia grade I, reactive atypia, or human papillomavirus infection alone or in combination was performed in a comparative evaluation of Feulgen microspectrophotometry, the fast interval processor image analysis system, and flow cytometry. The fast interval processor image analysis system showed a distinct advantage over the other methods, being faster and allowing the operator to see the cells that were selected for measurement. The three methods of measurement together showed that the DNA content of at least 2% of the cells measured exceeded 5C (C being the haploid amount of DNA in a normal cell and 2C representing the diploid complement of a normal cell) in all cases of cervical intraepithelial neoplasia grade I and reactive atypia and in 87% of those reported as showing human papillomavirus infection alone. In contrast, the DNA content of cervical biopsy specimens from the transformation zone of 11 normal controls did not exceed 4C. This study shows the value of using a DNA threshold--that is, the "5C exceeding rate"--to distinguish between normal and neoplastic appearances of the cervix. These results support the view that cervical infection by human papillomavirus is a true precursor of neoplasia.     

N-succinimidyl methoxyphenylacetic acid ester, an amine-directed chiral derivatizing reagent suitable for enzymatic scale resolutions

A chiral derivatizing reagent, N-succinimidyl-2-(S)-methoxy-2-phenylacetic acid ester (SMPA), directed toward reaction with primary amine-containing compounds has been synthesized and characterized. This reagent is suitable for HPLC resolution from enzymatic-scale reactions where only microgram quantities of chiral products may be obtainable. SMPA derivatization was shown to be effective in the resolution of the enantiomers of a number of different racemic compounds. SMPA was used to resolve the diastereoisomeric derivatives of a previously unknown enzymatically oxygenated product, allowing determination of the stereochemical course of the enzymatic reaction. SMPA is easily prepared from an inexpensive, commercially available, and enantiomerically pure precursor with the formation of a shelf-stable crystalline product which is utilizable in water-containing solutions. In addition to its usefulness for micro-determinations, SMPA is useful for preparative-scale resolutions of enantiomers since the reagent is cleaved from the diastereoisomeric derivative by acid hydrolysis.     

Unusual redox properties of electron-transfer flavoprotein from Methylophilus methylotrophus

The most positive redox potential ever recorded for a flavin adenine dinucleotide (FAD) containing protein has been measured for an electron-transfer flavoprotein (ETF) synthesized by Methylophilus methylotrophus. This potential value, 0.196 V versus the standard hydrogen electrode (vs SHE), was measured at pH 7.0 for the one-electron reduction of fully oxidized ETF (ETFox) to the red anionic semiquinone form of ETF (ETF.-). Quantitative formation of ETF.- was observed. The first successful reduction of ETF from M. methylotrophus to its two-electron fully reduced form was also achieved. Although addition of the second electron to ETF.- was extremely slow, the potential value measured for this reduction was -0.197 V vs SHE, suggesting a kinetic rather than thermodynamic barrier to two-electron reduction. These data are believed to be consistent with the postulated catalytic function of ETF to accept one electron from the iron-sulfur cluster of trimethylamine dehydrogenase (TMADH). The second electron reduction appears to have no catalytic function. The very positive potential measured for this ETF and the wide separation of potentials for the two electron reduction steps show that this ETF is a unique and interesting flavoprotein. In addition, this work highlights that while ETFs exhibit similar structural and spectral properties, they display wide variations in redox properties.     

Hydrolysis ofγ-glutamyl linkages byFusobacterium nucleatum

The cell extracts of two human oral strains (FN2 and FN3) ofFusobacterium nucleatum displayed exceptionally high-glutamylpeptidase activity as determined withN--l-glutamyl-2-naphthylamine as substrate. This activity was so dominant that the hydrolysis of otherN-aminoacyl-2-naphthylamines progressed at a rate <10% of the former. Two major enzymes (I and II) were partially purified from FN2. I had a molecular weight of 115,000 and did not hydrolyze-glutamylcysteinylglycine (glutathione). II had a molecular weight of 70,000 and rapidly liberated only glutamic acid from glutathione. Strain FN3 contained several enzymes hydrolyzing-glu-2NA. Direct anion exchange chromatography of FN3 cell extracts separated one enzyme that liberated both glutamic acid and glycine from glutathione, one that was inactive against glutathione (but hydrolyzed-glu-2NA), and one that liberated only glutamic acid. Although-glu-2NA was a good synthetic substrate, glutathione was hydrolyzed at least 500 times faster by an enzyme present in both strains. These results indicate that the presence of-glutamylpeptidase activity is very characteristic of theseF. nucleatum strains.     

The use of the probit model to predict pregnancy status of buffalo based on physio-chemical properties of estrual mucus

Improper timing of artificial insemination with respect to ovulation is one of the major factors hampering the conception rate in buffalo. The present study was an attempt to relate physio-chemical changes in estrual mucus to subsequent pregnancy status in order to find their optimal values for determining the time for artificial insemination (AI). Serum estradiol, total protein and dry matter contents of estrual mucus were evaluated to predict the subsequent pregnancy in 36 buffalo during October 1988 to February 1989. Serum estradiol was determined by radioimmunoassay (RIA); spinnbarkeit, dry matter and total protein were determined by standard methods. Multivariate probit analyses were carried out to relate these variables to subsequent pregnancy status. Elasticity and protein concentration were significantly related to prediction probability of pregnancy status, and they predicted the pregnancy status 86% of the times correctly (P < 0.05). The probability of pregnant animals being correctly classified was 0.76, whereas the corresponding value for non-pregnant animals was 0.95. The present study demonstrated the possibility of using such a statistical model on mucus characteristics for determining proper AI time for better conception rates in Nili-Ravi water buffalo.