Structural motifs for pyridoxal-5'-phosphate binding in decarboxylases: an analysis based on the crystal structure of the Lactobacillus 30a ornithine decarboxylase.

Two of the five domains in the structure of the ornithine decarboxylase (OrnDC) from Lactobacillus 30a share similar structural folds around the pyridoxal-5''-phosphate (PLP)-binding pocket with the aspartate aminotransferases (AspATs). Sequence comparisons focusing on conserved residues of the aligned structures reveal that this structural motif is also present in a number of other PLP-dependent enzymes including the histidine, dopa, tryptophan, glutamate, and glycine decarboxylases as well as tryptophanase and serine-hydroxymethyl transferase. However, this motif is not present in eukaryotic OrnDCs, the diaminopimelate decarboxylases, nor the Escherichia coli or oat arginine decarboxylases. The identification and comparison of residues involved in defining the different classes are discussed.     

Synchronous DNA synthesis and mitosis in multinucleate cells with one chromosome in each nucleus

Multinucleate cells were induced by colcemid treatment in PtK1 cells in culture. DNA synthesis and mitotic behavior of those cells in which each nucleus contained a single chromosome were studied. More than 80% of such cells showed synchronous DNA synthesis and mitosis in all nuclei. As these genetically different nuclei respond identically to the molecules that initiate DNA synthesis and mitosis, intranuclear control of initiation of DNA synthesis and induction of mitosis by genes on individual chromosomes can be excluded. The occasional occurrence of asynchronous division in multinucleate cells is assumed to result from unequal availability of the inducer molecules to the individual nuclei.     

Adsorption of Eu3+ and Am3+ ion towards hard donor-based diglycolamic acid-functionalised carbon nanotubes: density functional theory guided experimental verification

Structure, bonding, energetic and thermodynamic parameters of trivalent Eu³⁺ and Am³⁺ with diglycolamic acid-functionalised carbon nanotubes (CNT–DGA) in gas and solvent phases are reported in order to understand their complexation and extraction behaviour. The calculation was performed with generalised gradient approximated BP86 density functional and hybrid B3LYP functional using SVP/TZVP basis set. The free energy of extraction, ΔG_ext, of Eu³⁺ and Am³⁺ was computed using the Born–Haber thermodynamic cycle in conjunction with conductor-like screening model solvation approach. The calculated free energy of extraction was found to be exergonic using an explicit cluster water model for hydrating the ions and it was found to be higher for Eu³⁺ ion over Am³⁺ ion. From the estimated distribution constant using synthesised CNT–DGA, it is indisputably established that the Eu³⁺ ion is preferentially extracted over Am³⁺ ion and hence confirms the acceptance of the explicit cluster model for ion solvation free energy and thermodynamic cycle for the evaluation of free energy of extraction in solution phase. This is perhaps the first of its kind that a combined theoretical and experimental study has been performed on the free energy of extraction of Eu³⁺ and Am³⁺ using CNT–DGA.     

Synapsis in phage Bxb1 integration: selection mechanism for the correct pair of recombination sites

Recombination by site-specific recombinases is a highly concerted process that requires synapsis of the correct pair of DNA substrates. Phage-encoded serine-integrases are unusual among the serine-recombinase family, which includes transposon resolvases and DNA invertases, in that they utilize two simple but different DNA substrates (attB and attP) and do not require accessory sites, additional proteins, or DNA supercoiling. Synapsis must therefore be directed solely by integrase-DNA interactions. We show here that the Bxb1 serine-integrase binds as a dimer to its two DNA substrates (attB, attP) and recombinant products (attL, attR) with similar affinities. However, synapsis occurs only between attP and attB, and not between any of the other nine possible site combinations. The Bxb1 integrase domain structure, the unusual DNA-binding properties of the integrase, and the characterization of a mutant protein with altered site-discrimination, are consistent with synaptic selectivity being derived from DNA sequence-induced changes in the conformations of integrase-DNA complexes.     

Comparison of BMI and percentage of body fat of Indian and German children and adolescents

Today, serious health problems as overweight and obesity are not just constricted to the developed world, but also increase in the developing countries (Prentice 2006, Ramachandram et al. 2002). Focusing on this issue, BMI and percentage of body fat were compared in 2094 schoolchildren from two cross-sectional studies from India and Germany investigated in 2008 and 2009. The German children are in all age groups significantly taller, whereas the Indian children show higher values in BMI (e.g. 12 years: Indian: around 22 kg/m2; German: around 19 kg/m2) and in the percentage of body fat (e.g. 12 years: Indian: around 27%; German: around 18-20%) in most of the investigated age groups. The Indian children have significantly higher BMI between 10 and 13 (boys) respectively 14 years (girls). Indian children showed significant higher percentage of body fat between 10 and 15 years (boys) and between 8 and 16 years (girls). The difference in overweight between Indian and German children was strongest at 11 (boys) and 12 (girls) years: 70% of the Indian but 20% of the German children were classified as overweight. In countries such as India that undergo nutritional transition, a rapid increase in obesity and overweight is observed. In contrast to the industrialized countries, the risk of overweight in developing countries is associated with high socioeconomic status. Other reasons of the rapid increase of overweight in the developing countries caused by different environmental or genetic factors are discussed.     

Functional characterization of recombinant human granulocyte colony stimulating factor (hGMCSF) immobilized onto silica nanoparticles

Objectives

Granulocyte macrophage colony stimulating factor (GMCSF), an important therapeutic cytokine, was immobilized onto silica nanoparticles. Maintenance of structural integrity and biological performance in immobilized cytokine was assessed to augment its applicability in possible biomedical implications.

Results

Following its cloning and expression in E. coli, the recombinant human GMCSF (hGMCSF) was purified as a GST-tagged protein corresponding to a 42 kDa band on SDS-PAGE. The purified cytokine was immobilized onto biocompatible silica nanoparticles (~129.4 nm) by adsorption and the binding was confirmed by dynamic light scattering and infrared spectroscopy. Maximum binding of hGMCSF was at 6.4 µg mg^?1 silica nanoparticles. Efficient release of the cytokine from the nanoparticles with its structural integrity intact was deduced from circular dichroism spectroscopy. hGMCSF-immobilized silica nanoparticles efficiently increased the proliferation of RAW 264.7 macrophage cells with 50 % increase in proliferation at 600 ng hGMCSF µg^?1 silica nanoparticles.

Conclusions

Silica nanoparticles successfully immobilized hGMCSF maintaining its structural integrity. The release of the immobilized cytokine from silica nanoparticles resulted in the increased proliferation of macrophages indicating the potential of the system in future applications.