Electrosynthesis of yttrium from non-aqueous bath

93-94Electrodeposition of yttrium has been carried out from formaldehyde bath onto different substrates such as stainless steel, copper, brass, titanium and Indium Tin Oxide (ITO) coated glass. The deposition potentials are found to be substrate, solvent and complexing' agent dependent. Sodium acetate was found to be a suitable complexing agent for the depositon. Uniform and white gray films of yttrium of thickness between 0.4-0.5 micons have been doposited.</span

Structural and functional insights into the catalytic inactivity of the major fraction of buffalo milk xanthine oxidoreductase.

BACKGROUND: Xanthine oxidoreductase (XOR) existing in two interconvertible forms, xanthine dehydrogenase (XDH) and xanthine oxidase (XO), catabolises xanthine to uric acid that is further broken down to antioxidative agent allantoin. XOR also produces free radicals serving as second messenger and microbicidal agent. Large variation in the XO activity has been observed among various species. Both hypo and hyper activity of XOR leads to pathophysiological conditions. Given the important nutritional role of buffalo milk in human health especially in south Asia, it is crucial to understand the functional properties of buffalo XOR and the underlying structural basis of variations in comparison to other species. METHODS AND FINDINGS: Buffalo XO activity of 0.75 U/mg was almost half of cattle XO activity. Enzymatic efficiency (k cat/K m) of 0.11 sec(-1) µM(-1) of buffalo XO was 8-10 times smaller than that of cattle XO. Buffalo XOR also showed lower antibacterial activity than cattle XOR. A CD value (Δε430 nm) of 46,000 M(-1) cm(-1) suggested occupancy of 77.4% at Fe/S I centre. Buffalo XOR contained 0.31 molybdenum atom/subunit of which 48% existed in active sulfo form. The active form of XO in buffalo was only 16% in comparison to ∼30% in cattle. Sequencing revealed 97.4% similarity between buffalo and cattle XOR. FAD domain was least conserved, while metal binding domains (Fe/S and Molybdenum) were highly conserved. Homology modelling of buffalo XOR showed several variations occurring in clusters, especially close to FAD binding pocket which could affect NAD(+) entry in the FAD centre. The difference in XO activity seems to be originating from cofactor deficiency, especially molybdenum. CONCLUSION: A major fraction of buffalo milk XOR exists in a catalytically inactive form due to high content of demolybdo and desulfo forms. Lower Fe/S content and structural factors might be contributing to lower enzymatic efficiency of buffalo XOR in a minor way

Percent sequence identity of various domains of buffalo XOR with goat and human XOR at amino acid level.

<p>Percent sequence identity of various domains of buffalo XOR with goat and human XOR at amino acid level.</p

Comparison of molecular properties of buffalo and cattle milk XORs.

*<p>Data where reference is not cited were obtained in the present study.</p>†<p>The data have been shown as mean ± standard deviation. The number of experimental replicates have been shown as <i>n</i> in the text.</p

Antimicrobial activity of XOR.

<p>The open symbol (○) indicates cattle XOR activity whereas solid symbol (•) indicates buffalo XOR activity.</p

The α-carbon trace models of monomeric XOR.

<p>Panel A shows buffalo XOR while Panel B shows cattle XOR. The solid green color surface indicates the FAD molecule, the two 2Fe-2S (Fe/S) cofactor have been shown in space filling atomic representation in green (sulfur) and magenta (iron) color, while the Molybdenum cofactor (Moco) has been shown in ball and stick representation. The magenta color loop in buffalo XOR model, which is absent in electron density map of template cattle model (PDB ID: 3AMZ), connects the Fe/S domain (red color) with FAD domain (yellow color). The extended loop (residues 528–589) shown in green color connects the FAD domain with Moco domain (blue color). The residues shown with labels in buffalo XOR (Panel A) are only those which differed from corresponding residues in cattle XOR (Panel B) and also shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087618#pone-0087618-t003" target="_blank">Table 3</a>. In case of template cattle XOR model, several loop structures were missing, which were built for buffalo XOR as described in the text.</p

Michaelis-Menten kinetics of buffalo milk XOR for the conversion of xanthine to uric acid.

<p>Panel A shows the Michaelis-Menten and Lineweaver–Burk plots (inset) for XO activity in the air saturated reaction buffer and, Panel B shows corresponding plots for XDH activity in the presence of NAD⁺ in the reaction mixture.</p

Near UV/visible CD spectrum of buffalo milk XOR.

<p>The CD spectrum has been normalized on the basis of FAD content to subunit concentration of 1.0</p

Amino acid variations in various domains of buffalo and cattle XOR.

†<p>Different residue numbering has been shown where buffalo and cattle XOR residues differed because of insertion/deletion events. The first number belongs to buffalo XOR residue while second number belongs to cattle XOR residue.</p