RESUMO
Genes at the centromeric end of the human leukocyte antigen region influence adaptive autoimmune diseases and cancer. In this study, we characterized protein expression of HKE2, a gene located in the centromeric portion of the class II region of the major histocompatibility complex encoding subunit 6 of prefoldin. Immunohistochemical analysis using an anti-HKE2 antibody indicated that HKE2 protein expression is dramatically upregulated as a consequence of activation. In a tissue microarray and in several tumors, HKE2 was overexpressed in certain cancers compared with normal counterparts. The localization of the HKE2 gene to the class II region, its cytoplasmic expression and putative protein-binding domain suggest that HKE2 may function in adaptive immunity and cancer.
Assuntos
Genes MHC da Classe II/genética , Chaperonas Moleculares/metabolismo , Neoplasias/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Mapeamento Cromossômico , Citoplasma/química , Células-Tronco Hematopoéticas/química , Células-Tronco Hematopoéticas/metabolismo , Humanos , Imuno-Histoquímica , Chaperonas Moleculares/análise , Chaperonas Moleculares/genética , Dados de Sequência Molecular , Neoplasias/química , Conformação Proteica , Células Tumorais CultivadasRESUMO
The design, synthesis, and complexation characteristics of the bipyridyl ligand 1,2-bis-(2-pyridylethynyl)benzene are described. The X-ray crystallographic characterization of the 1:1 complexes of 1,2-bis(2-pyridylethynyl)benzene with silver(I) triflate and palladium(II) chloride are described. In the X-ray crystal structure of the silver(I) triflate complex the ligand is essentially planar with negligible distortion compatible with a good fit of the cation in the "cavity" between the pyridine N atoms. Indeed the silver center is almost linear with the N(1)-Ag(1)-N(2) angle of 177.02(10) degrees. The ligand is also essentially planar in the palladium(II) chloride complex with square planar coordination about the palladium with the N(1)-Pd(1)-N(2), Cl(2)-Pd(1)-Cl(2), and N(1)-Pd(1)-Cl(2) angles at 179.53(7), 177.17(2), and 90.52(5) degrees, respectively.
RESUMO
Tirapazamine (1) is a promising antitumor agent that selectively causes DNA damage in hypoxic tumor cells, following one-electron bioreductive activation. Surprisingly, after more than 10 years of study, the products arising from bioreductive metabolism of tirapazamine have not been completely characterized. The two previously characterized metabolites are 3-amino-1,2,4-benzotriazine 1-oxide (3) and 3-amino-1,2,4-benzotriazine (5). In this work, 3-amino-1,2,4-benzotriazine 4-oxide (4) is identified for the first time as a product resulting from one-electron activation of the antitumor agent tirapazamine by the enzymes xanthine/xanthine oxidase and NADPH:cytochrome P450 oxidoreductase. As part of this work, the novel N-oxide (4) was unambiguously synthesized and characterized using NMR spectroscopy, UV-vis spectroscopy, LC/MS, and X-ray crystallography. Under conditions where the parent drug tirapazamine is enzymatically activated, the metabolite 4 is produced but readily undergoes further reduction to the benzotriazine (5). Thus, under circumstances where extensive reductive metabolism occurs, the yield of the 4-oxide (4) decreases. In contrast, the isomeric two-electron reduction product 3-amino-1,2,4-benzotriazine 1-oxide (3) does not readily undergo enzymatic reduction and, therefore, is found as a major bioreductive metabolite under all conditions. Finally, the ability of the 4-oxide metabolite (4) to participate in tirapazamine-mediated DNA damage is considered.
Assuntos
Antineoplásicos/farmacocinética , Triazinas/síntese química , Triazinas/farmacocinética , Antineoplásicos/química , Cromatografia Líquida de Alta Pressão , Dano ao DNA/efeitos dos fármacos , Indicadores e Reagentes , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , NADPH-Ferri-Hemoproteína Redutase/metabolismo , Oxirredução , Tirapazamina , Triazinas/química , Xantina Oxidase/metabolismoRESUMO
The bidentate, water-soluble phosphine ligands, bis(bis(hydroxymethyl)phosphino)benzene (HMPB, 1) and bis(bis(hydroxymethyl)phosphino)ethane (HMPE, 2) were reacted with the organometallic precursor fac-[ReBr(3)(CO)(3)](2-), 3, to produce the complexes fac-[Re(OH(2))(CO)(3)L](+) and fac-[ReBr(CO)(3)L] (L = HMPE, HMPB), respectively, in good yields. The rhenium complexes fac-[ReBr(CO)(3)HMPB], 5, and fac-[ ReBr(CO)(3)HMPE], 8, were characterized using (1)H and (31)P NMR spectroscopy. The structure of fac-[ReBr(CO)(3)HMPB] was confirmed by single-crystal X-ray spectroscopy. The substitution reactions of HMPE/HMPB with the rhenium precursor 3 in aqueous solution were monitored using time-dependent (31)P NMR techniques. A significant discrepancy in the reaction kinetics and the substitution mechanism between the two bidentate ligands could be observed presumably due to the different chemical backbones.
Assuntos
Compostos Organometálicos/química , Compostos Radiofarmacêuticos/química , Cristalografia por Raios X , Espectroscopia de Ressonância MagnéticaRESUMO
The molecular complex formed between 4-methyltolane and bis(4-N-methylpyridinium)ethyne ditriflate is reported. The X-ray crystal structure indicates that the crystalline superstructure consists of infinite zigzag ribbons of interlocked donor-acceptor complexes separated by triflate counterions.
Assuntos
Hidrocarbonetos Aromáticos com Pontes/síntese química , Cnidários/química , Lactonas/síntese química , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Toxinas Marinhas/síntese química , Toxinas Marinhas/químicaRESUMO
Four diterpenes and a nor-diterpenoid, all of which possess unusual carbocyclic skeletons, were isolated from the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae. The structures and relative configurations of novel metabolites elisabethin D (2), elisabethin D acetate (3), 3-epi-elisabanolide (5), elisapterosin A (6), and elisapterosin B (7) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS), chemical reactions, and X-ray diffraction analyses. The tetracyclic carbon skeleton of the elisapterosins is undescribed and constitutes a new class of C(20) rearranged diterpenes. Elisapterosin B displays strong in vitro anti-tuberculosis activity.
Assuntos
Cnidários/química , Diterpenos/química , Animais , Antituberculosos/química , Antituberculosos/isolamento & purificação , Antituberculosos/metabolismo , Antituberculosos/farmacologia , Hidrocarbonetos Aromáticos com Pontes/química , Cristalografia por Raios X , Diterpenos/isolamento & purificação , Diterpenos/metabolismo , Diterpenos/farmacologia , Humanos , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação Molecular , Estrutura Molecular , Mycobacterium tuberculosis/efeitos dos fármacos , Compostos Policíclicos/química , Células Tumorais Cultivadas , Índias OcidentaisRESUMO
The 2.1 A resolution crystal structure of flavin reductase P with the inhibitor nicotinamide adenine dinucleotide (NAD) bound in the active site has been determined. NAD adopts a novel, folded conformation in which the nicotinamide and adenine rings stack in parallel with an inter-ring distance of 3.6 A. The pyrophosphate binds next to the flavin cofactor isoalloxazine, while the stacked nicotinamide/adenine moiety faces away from the flavin. The observed NAD conformation is quite different from the extended conformations observed in other enzyme/NAD(P) structures; however, it resembles the conformation proposed for NAD in solution. The flavin reductase P/NAD structure provides new information about the conformational diversity of NAD, which is important for understanding catalysis. This structure offers the first crystallographic evidence of a folded NAD with ring stacking, and it is the first enzyme structure containing an FMN cofactor interacting with NAD(P). Analysis of the structure suggests a possible dynamic mechanism underlying NADPH substrate specificity and product release that involves unfolding and folding of NADP(H).
Assuntos
NADH NADPH Oxirredutases/química , NADH NADPH Oxirredutases/metabolismo , NAD/química , NAD/metabolismo , Dobramento de Proteína , Sítios de Ligação , Cristalografia por Raios X , Dimerização , FMN Redutase , Análise dos Mínimos Quadrados , Substâncias Macromoleculares , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Vibrio/enzimologiaRESUMO
The title compound, C15H9BrN2O3S, was isolated as an unexpected product from the reaction of the anion of sodium 2-(1,3-benzothiazolyl)ethanonitrile with alpha,2-dibromo-5-nitrotoluene. Its structure features a benzothiazole fragment and a bromo- and nitro-substituted phenyl ring linked by a methyl ketone group. The dihedral angle between the benzothiazole and phenyl rings is 103.7 (2) degrees. The benzothiazole fragment is planar, with a maximum deviation of 0.021 (2) A. The nitro group is slightly rotated out of the phenyl-ring plane, with a O(2)-N(2)-C(14)-C(15) torsion angle of 16.4(7) degrees.
Assuntos
Tiazóis/química , Acetonitrilas , Benzotiazóis , Cristalização , Cristalografia por Raios X , Modelos Moleculares , Estrutura MolecularRESUMO
Calyxamines A (1) and B (2) are 2,2,4,6,6-pentasubstituted piperidine alkaloids possessing novel carbon skeletons isolated from the marine sponge Calyx podatypa collected in Puerto Rico. Their structures, after derivatization with trifluoroacetic acid, have been determined by a combination of X-ray and spectroscopic methods. A plausible biogenetic pathway to the calyxamines is suggested.
Assuntos
Alcaloides/isolamento & purificação , Piperidinas/isolamento & purificação , Poríferos/química , Alcaloides/química , Animais , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Piperidinas/químicaAssuntos
Acidose Láctica/congênito , Acidose Láctica/tratamento farmacológico , Ácido Dicloroacético/uso terapêutico , Acidose Láctica/genética , Adolescente , Criança , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Mutação , Doença da Deficiência do Complexo de Piruvato Desidrogenase/genéticaRESUMO
Thirty-one consecutive open fractures of the tibia were reviewed prospectively. Duration from injury until last examination averaged 3.7 years. The patients were divided into 2 groups for comparison: Group A consisted of children younger than 12 years of age and Group B of patients 12 years of age or older. The fractures were graded according to the system of Gustilo and Anderson. The severity of patient injuries in each group was similar. The treatments were likewise similar, but for all parameters studied, the younger patients fared better than their older counterparts. This study suggests that open fractures in children younger than 12 years of age require less aggressive surgical treatment, heal faster, are more resistant to infection, and have fewer complications than those in older children.
Assuntos
Envelhecimento/fisiologia , Consolidação da Fratura/fisiologia , Fraturas Expostas/fisiopatologia , Fraturas da Tíbia/fisiopatologia , Adolescente , Criança , Pré-Escolar , Humanos , Prognóstico , Estudos RetrospectivosRESUMO
Crystals of a 26-nucleotide pseudoknot RNA, PK26, have been grown. The RNA was produced using phosphoramidite chemistry and was purified by denaturing polyacrylamide electrophoresis. The crystallization was robust with respect to changes in the number of nucleotides and to the salt used as precipitant. The crystals belong to space group P4(1)22 or P4(3)22 with unit-cell dimensions a = b = 61.6, c = 98.9 A. The best crystals diffract X-rays to 2.9 A. Three different sequences incorporating a single 5-bromo-deoxyuridine or 5-bromo-uridine nucleotide were also crystallized. Two of these derivatives are being used to determine the structure by multiple isomorphous replacement.
RESUMO
BACKGROUND: Non-canonical base pairs are fundamental building blocks of RNA structures. They can adopt geometries quite different from those of canonical base pairs and are common in RNA molecules that do not transfer sequence information. Tandem U-U base pairs occur frequently, and can stabilize duplex formation despite the fact that a single U-U base pair is destabilizing. RESULTS: We determined the crystal structure of the RNA dodecamer GGCGCUUGCGUC at 2.4 A resolution. The molecule forms a duplex containing tandem U-U base pairs, which introduce an overall bend of 11-12 degrees in the duplex resulting from conformational changes at each interface between the tandem U-U base pairs and a flanking duplex sequence. The formation of the U-U base pairs cause small changes in several backbone torsion angles; base stacking is preserved and two hydrogen bonds are formed per base pair, explaining the stability of the structure. CONCLUSIONS: Tandem U-U base pairs can produce stable structures not accessible to normal A-form RNA, which may allow the formation of specific interfaces for RNA-RNA or RNA-protein recognition. These base-pairs show an unusual pattern of hydrogen-bond donors and acceptors in the major and minor grooves, which could also act as a recognition site.