Theoretical studies of biliverdin: energetics of the reduction pathways to bilirubin

Geometries and energies of formation of bilirubin formed by reduction of biliverdin via three meso carbon sites, the , and positions, have been calculated using semiempirical methods. It has been shown that -bilirubin with a ridge-tile conformation forms six intramolecular hydrogen bonds and is the most stable of the three above mentioned positions by at least 22 kcal mol^–1. Reduction pathways for -, - and -bilirubin formations from biliverdin are studied in detail. The roles of loss of conjugation and hydrogen bond formations in stability of different conformers have been discussed. -Bilirubin was fully optimized by using ab initio methods. Fine refinements of calculated results show excellent agreement with experimental results. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00894-002-0078-9.Electronic Supplementary Material available.     

The HIV-1 accessory protein Nef increases surface expression of the checkpoint receptor Tim-3 in infected CD4+ T cells

Prolonged immune activation drives the upregulation of multiple checkpoint receptors on the surface of virus-specific T cells, inducing their exhaustion. Reversing HIV-1-induced T cell exhaustion is imperative for efficient virus clearance; however, viral mediators of checkpoint receptor upregulation remain largely unknown. The enrichment of checkpoint receptors on T cells upon HIV-1 infection severely constrains the generation of an efficient immune response. Herein, we examined the role of HIV-1 Nef in mediating the upregulation of checkpoint receptors on peripheral blood mononuclear cells. We demonstrate that the HIV-1 accessory protein Nef upregulates cell surface levels of the checkpoint receptor T-cell immunoglobulin mucin domain-3 (Tim-3) and that this is dependent on Nef''s dileucine motif LL_164/165. Furthermore, we used a bimolecular fluorescence complementation assay to demonstrate that Nef and Tim-3 form a complex within cells that is abrogated upon mutation of the Nef dileucine motif. We also provide evidence that Nef moderately promotes Tim-3 shedding from the cell surface in a dileucine motif–dependent manner. Treating HIV-1-infected CD4⁺ T cells with a matrix metalloprotease inhibitor enhanced cell surface Tim-3 levels and reduced Tim-3 shedding. Finally, Tim-3-expressing CD4⁺ T cells displayed a higher propensity to release the proinflammatory cytokine interferon-gamma. Collectively, our findings uncover a novel mechanism by which HIV-1 directly increases the levels of a checkpoint receptor on the surface of infected CD4⁺ T cells.     

A gene for lymphedema-distichiasis maps to 16q24.3.

Lymphedema-distichiasis (LD) is a dominantly inherited syndrome with onset of lymphedema at or just after puberty. Most affected individuals have distichiasis-fine hairs arising inappropriately from the eyelid meibomian glands-which is evident from birth. A study of three families with LD has shown linkage to chromosome 16q24.3, and subsequent analysis of the region for recombinant genes places the locus between D16S422 and D16S3074, a distance of approximately 16 cM. Possible candidate genes in this interval include the N-proteinase for type 3 collagen, PCOLN3; the metalloprotease PRSM1; and the cell matrix-adhesion regulator, CMAR.     

Trochelioid A and B,new cembranoid diterpenes from the Red Sea soft coral Sarcophyton trocheliophorum

Chemical investigations of the soft coral Sarcophyton trocheliophorum, has led to the isolation of six cembranoids, two of which are new, Trochelioid A (1) and B (2), and one, 16-oxosarcophytonin E (3) isolated from nature for the first time. Additionally, two have been isolated from S. trocheliophorum for the first time (4 and 6). Structures were elucidated by employing extensive NMR and HR-FAB-MS experimentation.     

Semisynthesis of some novel thiourea and carbamimidothioic acid derivatives using natural alkaloid L-norephedrine and their anticancer activity

A novel series of thiourea and carbamimidothioic acid derivatives was synthesized using natural alkaloid L-norephedrine as a starting material. Structures of the newly synthesized compounds were confirmed by analytical and spectral data. The synthesized compounds were evaluated in vitro for anticancer activity against the human breast (MCF-7), human liver (HEPG2), and human colon (HCT116) cancer cell lines. Best activity of the synthesized compounds was expressed against HEPG2, however, none of the compounds exceeded the IC₅₀ of doxorubicin. The corresponding N-(1-(2-chloroacetoxy)-1-phenylpropan-2-yl)-N′-p-tolylcarbamimidothioic acid was the most potent compound and exhibited higher cytotoxic activity against the human colon cancer cell line (HCT116) when compared with the reference drug doxorubicin. Also, this compound was the most active against the MCF-7 cell line but less active than the positive control.     

Melanism and coat colour polymorphism in the Egyptian Wolf Canis lupaster Hemprich & Ehrenberg (Carnivora: Canidae) from Egypt

The Egyptian Wolf Canis lupaster was recently rediscovered as a distinct species on the basis of both morphologic and molecular genetic evidence. Phenotypical variability, including coat colour of this species across its vast, ecologically diverse range is yet to be investigated. In this paper, we present the first record of melanistic individuals of this species and compare their morphological characters and mitochondrial cytochrome b DNA sequences with those of typically coloured Canis lupaster and other closely related canids to verify their identity. We also study pelage polymorphism in a population of this species in the Egyptian Nile Valley and the Nile Delta and define its different colour variants. The typical colour, as well as the rare, very light and reddish coat colours are described. We discuss the possibility that the observed coat colour polymorphism is the result of hybridisation with the domestic dog and their potential adaptive significance.     

A multifaceted approach to identify non-specific enzyme inhibition: Application to Mycobacterium tuberculosis shikimate kinase

Single dose high-throughput screening (HTS) followed by dose-response evaluations is a common strategy for the identification of initial hits for further development. Early identification and exclusion of false positives is a cost-saving and essential step in early drug discovery. One of the mechanisms of false positive compounds is the formation of aggregates in assays. This study evaluates the mechanism(s) of inhibition of a set of 14 compounds identified previously as actives in Mycobacterium tuberculosis (Mt) cell culture screening and in vitro actives in Mt shikimate kinase (MtSK) assay. Aggregation of hit compounds was characterized using multiple experimental methods, LC-MS, ¹HNMR, dynamic light scattering (DLS), transmission electron microscopy (TEM), and visual inspection after centrifugation for orthogonal confirmation. Our results suggest that the investigated compounds containing oxadiazole-amide and aminobenzothiazole moieties are false positive hits and non-specific inhibitors of MtSK through aggregate formation.