Molecules In Asymmetric Unit Cell Research Articles

Synthesis and characterization of n-alkylamino derivatives of vitamin K3: Molecular structure of 2-propylamino-3-methyl-1,4-naphthoquinone and antibacterial activities

We would like to introduce eight analogues of n-alkylamino derivatives of vitamin K3 (2-methyl-1,4-naphthoquinone) viz, 2-(n-alkylamino)-3-methyl-1,4-naphthoquinone (where n-alkyl is methyl; LM-1, ethyl; LM-2, propyl; LM-3, butyl; LM-4, pentyl; LM-5, hexyl; LM-6, heptyl; LM-7, octyl; LM-8). All the above analogues have been successfully synthesized from vitamin K3 and characterized using different analytical techniques. Furthermore, in order to understand the mechanistic aspects of formation of LM-1 to LM-8 compounds, we could propose the mechanism. The FT-IR analysis of LM-1 to LM-8 indicate the presence of characteristic band of NH group ∼3287–3364cm−1, the variation was attributed to extensive intramolecular hydrogen bonding interaction. The molecular structure of LM-3 compound has been confirmed by single crystal X-ray diffraction analysis. LM-3 compound crystallises in triclinic space group P1. There were four independent molecules in asymmetric unit cell and their molecular interactions observed via NH⋯O, CH⋯O and π–π stacking of quinonoid rings. Pharmacological potential of all compounds has been evaluated in terms of their antibacterial activities against Pseudomonas aeruginosa and Staphylococcus aureus. All the compounds were active against both the strains while LM-2 was found to be more effective with a minimum inhibition concentration of 0.3125μg/mL and 0.156μg/mL respectively.

Structure of Crohn'S Disease-Related Proteins and their Binding to Class II MHC

T cell response to enteric bacteria is important in inflammatory bowel disease. pfiT is a T-cell superantigen associated with human Crohn's disease. The bacterial superantigens are a class of protein toxins that share the capacity to induce massive activation of the human immune system. These molecules simultaneously bind to major histocompatibility complex class II molecules on the surface of antigen-presenting cells and T-cell receptors (TCRs) on T cells to stimulate large numbers of T cells. The aim of this study is to analyze the molecular mechanism of superantigen recognition by host receptors. Here, we report the crystal structure of pfiT. This protein was overexpressed in Escherichia coli and purified though GST-affinity and size exclusion chromatography. The protein is selenomethionine labeled and single wavelength anomalous dispersion method was used for determination of the crystal structure. The superantigen crystallizes in the monoclinic space group P21, with two molecules in asymmetric unit cell. The structure was determined to 2.5A resolution. In addition, we performed radiolabeled competitive binding assays between three superantigens: pfiT, Mycoplasma arthritidis-derived mitogen (MAM), PA2885, a novel open reading frame (ORF) in the Pseudomonas aeruginosa genome. Analyses showed that both the microbial homologuepfit and PA2885, just as potent superantigen MAM, are capable of binding to target mammalian cells. Moreover, we labeled these superantigens with FITC and analyzed them by FACS in PBMC. The statistic results show that antibody against HLA-DR has strong effect to block these SAg' binding ability with PBMC, and antibodies against HLA-DQ and DP can also compete binding site in a much weaker manner. These findings support the concept that pfiT, PA2885, MAM are superantigens and can bind to class II MHC molecule .Research is funded by the Crohn’ & Colitis Foundation of America.

Crystal Structure of 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)quinazolin-4(3H)-one and its Ligating Diversity Towards Transition Metal(II) Ions

The synthesis of a new ligand 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)-quinazolin-4(3H)-one (PPCAQ) is described together with its manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes. The single crystal X-ray diffraction studies of the ligand reveal the presence of two crystallographically independent molecules in asymmetric unit cell, which exhibit N...N attractive interaction. The PPCAQ and its metal complexes were characterized by analytical, spectroscopic (i.r., n.m.r and u.v.-vis), magnetic moment, conductance and thermal studies. The i.r. spectral studies reveal the ligational diversity of the PPCAQ towards different metal ions as NNN donor in cobalt(II), copper(II), zinc(II) and cadmium(II) complexes and as ONN donor in manganese(II) and nickel(II) complexes. The antimicrobial activity of all the compounds was tested; copper(II), zinc(II) and cadmium(II) complexes show enhanced antibacterial activity compared to the free ligand.