Sandwich microgravimetric immunoassay: sensitive and specific detection of low molecular weight analytes using piezoelectric quartz crystal

A multi-channel sandwich microgravimetric immunoassay (sMIA), using the quartz crystal microbalance (QCM) principle, has been developed to quantify low molecular weight substances in standard solutions. An antigen is sandwiched between two antigen-specific antibodies: the first antibody is coated on the quartz crystal surface and the second antibody is used for the detection of analyte. The concentration of low molecular weight antigen (insulin was used in this study, M _r6000 Da) was correlated with the shift of resonant frequency of QCM system before and after second antibody binding to insulin. The developed assay is highly specific showing low cross-reactivity, and is sensitive to approx. 1 ng insulin ml^–1 with a linear response for insulin from 10 g ml^–1 to 10 ng ml^–1 in standard solutions. The technique may also be applied for the detection of other small biomolecules.     

Bacterial glycoproteins: functions,biosynthesis and applications

Although widely distributed in eukaryotic cells glycoproteins appear to be rare in prokaryotic organisms. The prevalence of the misconception that bacteria do not glycosylate their proteins has been a subject matter of discussion for a long time. Glycoconjugates that are linked to proteins or peptides, generated by the ribosomal translational mechanism have been reported only in the last two to three decades in a few prokaryotic organisms. Most studied prokaryotic glycoproteins are the S-layer glycoproteins of Archeabacteria. Apart from these, membrane-associated, surface-associated, secreted glycoproteins and exoenzymes glycoproteins are also well documented in both, Archea and Eubacteria. From the recent literature, it is now clear that prokaryotes are capable of glycosylating proteins. In general, prokaryotes are deprived of the cellular organelles required for glycosylation. In prokaryotes many different glycoprotein structures have been observed that display much more variation than that observed in eukaryotes. Besides following similar mechanisms in the process of glycosylation, prokaryotes have also been shown to use mechanisms that are different from those found in eukaryotes. The knowledge pertaining to the functional aspects of prokaryotic glycoproteins is rather scarce. This review summarizes developments and understanding relating to characteristics, synthesis, and functions of prokaryotic glycoproteins. An extensive summary of glycosylation that has been reported to occur in bacteria has also been tabulated. Various possible applications of these diverse biomolecules in biotechnology, vaccine development, pharmaceutics and diagnostics are also touched upon.     

Unusual presentation of choriocarcinoma

Background  

Choriocarcinoma is an aggressive neoplasm arising in the body of the uterus. The disease normally spreads to lung and brain.     

Central Mucoepidermoid carcinoma of mandible – A case report and review of the literature

BACKGROUND: Primary central mucoepidermoid carcinoma of jaws is a rare lesion comprising 2-3% of all mucoepidermoid carcinomas reported in literature. CASE PRESENTATION: The case presented here illustrates the hypothesis that its specific pathogenesis is unknown. CONCLUSIONS: Mucoepidermoid carcinoma of the jaw is a rare tumour of unknown aetiology. Although about a 100 cases has been reported in literature, the speculation on its aetiopathogenesis has mainly centred on the pluripotential capabilities of the epithelial lining of odontogenic cysts.     

Phenotypic variation of Plasmodium falciparum merozoite proteins directs receptor targeting for invasion of human erythrocytes

The members of the phylum Apicomplexa parasitize a wide range of eukaryotic host cells. Plasmodium falciparum, responsible for the most virulent form of malaria, invades human erythrocytes using several specific and high affinity ligand-receptor interactions that define invasion pathways. We find that members of the P. falciparum reticulocyte-binding homolog protein family, PfRh2a and PfRh2b, are expressed variantly in different lines. Targeted gene disruption shows that PfRh2b mediates a novel invasion pathway and that it functions independently of other related proteins. Phenotypic variation of the PfRh protein family allows P. falciparum to exploit different patterns of receptors on the erythrocyte surface and thereby respond to polymorphisms in erythrocyte receptors and to evade the host immune system.     

A Molecular Electrostatic Potential Mapping Study of Some Fluoroquinolone Anti-Bacterial Agents

Molecular electrostatic potential (MEP) maps of some fluoroquinolones having varying degrees of activity against the bacterium Staphylococcus Aureus have been studied using the optimized hybridization displacement charges (HDC) combined with Löwdin charges obtained by the AM1 method. The roles of different substitutions at the N₁-position in the parent quinolone ring have been studied. The conformation of the carboxylic group attached to the quinolone ring was shown to be such that there is an intramolecular hydrogen bonding between the hydrogen atom of this group and the oxygen atom of the carbonyl group of the quinolone moiety. The carbonyl oxygen atom of the quinolone moiety, hydroxyl oxygen atom of the carboxylic group and the terminal nitrogen atom of the piperazin ring attached to the quinolone ring appear to be involved in the action of the drugs through electrostatic interactions while the N₁-alkyl substituents seem to be involved in the same through hydrophobic interactions.     

Mutagenic analysis of putative domain II and surface residues in mosquitocidal Bacillus thuringiensis Cry19Aa toxin

The growing resistance against antibiotics demands the search for alternative treatment strategies. Photodynamic therapy is a promising candidate. The natural intermediate of chlorophyll biosynthesis, protochlorophyllide, was produced, purified and tested as a novel photosensitizer for the inactivation of five model organisms including Staphylococcus aureus, Listeria monocytogenes and Yersinia pseudotuberculosis , all responsible for serious clinical infections. When microorganisms were exposed to white light from a tungsten filament lamp (0.1 mW cm⁻²), Gram-positive S. aureus, L. monocytogenes and Bacillus subtilis were photochemically inactivated at concentrations of 0.5 mg L⁻¹ protochlorophyllide. Transmission electron microscopy revealed a disordered septum formation during cell division and the partial loss of the cytoplasmic cell contents. Gram-negative Y. pseudotuberculosis and Escherichia coli were found to be insensitive to protochlorophyllide treatment due to the permeability barrier of the outer membrane. However, the two bacteria were rendered susceptible to eradication by protochlorophyllide (10 mg L⁻¹) upon addition of polymyxin B nonapeptide at 50 and 20 mg L⁻¹, respectively. The release of DNA and a detrimental rearrangement of the cytoplasm were observed.     

Methotrexate Promotes Platelet Apoptosis via JNK-Mediated Mitochondrial Damage: Alleviation by N-Acetylcysteine and N-Acetylcysteine Amide

Thrombocytopenia in methotrexate (MTX)-treated cancer and rheumatoid arthritis (RA) patients connotes the interference of MTX with platelets. Hence, it seemed appealing to appraise the effect of MTX on platelets. Thereby, the mechanism of action of MTX on platelets was dissected. MTX (10 μM) induced activation of pro-apoptotic proteins Bid, Bax and Bad through JNK phosphorylation leading to ΔΨm dissipation, cytochrome c release and caspase activation, culminating in apoptosis. The use of specific inhibitor for JNK abrogates the MTX-induced activation of pro-apoptotic proteins and downstream events confirming JNK phosphorylation by MTX as a key event. We also demonstrate that platelet mitochondria as prime sources of ROS which plays a central role in MTX-induced apoptosis. Further, MTX induces oxidative stress by altering the levels of ROS and glutathione cycle. In parallel, the clinically approved thiol antioxidant N-acetylcysteine (NAC) and its derivative N-acetylcysteine amide (NACA) proficiently alleviate MTX-induced platelet apoptosis and oxidative damage. These findings underpin the dearth of research on interference of therapeutic drugs with platelets, despite their importance in human health and disease. Therefore, the use of antioxidants as supplementary therapy seems to be a safe bet in pathologies associated with altered platelet functions.