MMP-9和TIMP-1表达失衡与乳腺癌浸润、转移的相关性

目的 研究乳腺癌组织中基质金属蛋白酶（MMP－9）和金属蛋白酶组织抑制因子（TIMP－1）的表达变化与乳腺癌生物学行为及淋巴结转移的关系。方法 应用SP免疫组织化学方法检测85例乳腺癌组织MMP－9，TIMP－1及细胞增殖核抗原ki-67的表达情况。结果 MMP-9阳性染色率90．59％，MMP－9阳性表达与肿瘤浸润，淋巴结转移，ki-67指数及TNM分期呈正相关（Pearson列联系数分别为P=0.03,P=0.02,P=0.004和P＝0．0000，P＜0．05，0．01。TIMP－1阳性染色率为78．82％，TIMP－1阳性表达与肿瘤浸润，淋巴结转移及TNM分期浸润，转移及ki-67指数显著相关（P＜0．05，P＜0．01，P＜0．001）。结论 MMP－9和TIMP－1表达失衡与乳腺癌浸润及淋巴结转移密切相关。     

Inhibition of tumour necrosis factor-alpha (TNF-α)

Peptide deformylase (PDF) catalyses the hydrolytic removal of the N-terminal formyl group from nascent ribosome-synthesised polypeptides. Its activity is essential and it is present in all eubacteria. It is also present in the organelles of some eukaryotes. PDF represents a novel class of mononuclear iron protein, utilising an Fe²⁺ ion to catalyse the hydrolysis of an amide bond. Due to its extreme lability, isolation and characterisation of PDF was not possible until very recently. This review will discuss the recent progress in the elucidation of the the structure and function of PDF, evaluating its suitability as a target for antibiotic design and summarising the current approaches to designing drugs that target PDF.     

COPPER BIOAVAILABILITY: ASSESSMENT AND EXTRINSIC FACTORS

Copper bioavailability may be efficienty assessed using suckling rats, and is adversely affected in rats and human beings by fructose and excess dietary zinc.     

Mechanism of tungsten-dependent acetylene hydratase from quantum chemical calculations

Acetylene hydratase is a tungsten-dependent enzyme that catalyzes the nonredox hydration of acetylene to acetaldehyde. Density functional theory calculations are used to elucidate the reaction mechanism of this enzyme with a large model of the active site devised on the basis of the native X-ray crystal structure. Based on the calculations, we propose a new mechanism in which the acetylene substrate first displaces the W-coordinated water molecule, and then undergoes a nucleophilic attack by the water molecule assisted by an ionized Asp13 residue at the active site. This is followed by proton transfer from Asp13 to the newly formed vinyl anion intermediate. In the subsequent isomerization, Asp13 shuttles a proton from the hydroxyl group of the vinyl alcohol to the α-carbon. Asp13 is thus a key player in the mechanism, but also W is directly involved in the reaction by binding and activating acetylene and providing electrostatic stabilization to the transition states and intermediates. Several other mechanisms are also considered but the energetic barriers are found to be very high, ruling out these possibilities.     

ox-LDL对人血管平滑肌细胞间质胶原酶及TIMP-1基因表达的影响

目的 研究氧化低密度脂蛋白（ox-LDL)与维生素C（Vitamin,C,VC)对平滑肌间质胶原酶及TIMP－1基因表达的影响。方法 采用Northern印迹杂交法检测ox-LDL与VC对人血管平滑肌细胞MMP－1及TIMP－1基因表达的影响。结果 ox-LDL可明显增加平滑肌细胞MMP－1基因的表达，VC可削弱ox-LDL对MMP－1表达的诱导作用，未经修饰的脂蛋白（nLDL)及VC单独作用，对MMP－1基因的表达无明显影响。结论 ox-LDL参与动脉粥样硬化斑块中基质降解，使动脉粥样硬化斑块易于破裂，适当地摄入维生素C等抗氧化剂可预防斑块的破裂。     

Zinc Deficiency Impairs Ethanol Metabolism

Rats on a zinc-restricted diet had lower levels of hepatic alcohol dehydrogenase and slower rates of ethanol elimination than pair-fed controls.     

DESIGN,SYNTHESIS AND 13 C- AND 1 H-N.M.R. INVESTIGATION OF A CYCLIC OCTAPEPTIDE TO MIMIC THE ZINC-BINDING SITE OF CARBOXYPEPTIDASE A

Considering the three-dimensional structure and the native Zn(II)-binding ligands of carboxypeptidase A followed by extensive model building, a cyclic octapeptide, cyclo-(Gly-L-Glu-Gly-Gly-L-His-Gly-L-His-Gly) was designed to mimic the Zn(II)-binding site of carboxypeptidase A. The cyclic octapeptide was prepared by high dilution technique from the corresponding linear octapeptide, N-Boc-Gly-γ-OBu^t-L-Glu-Gly-Gly-L-His-Gly-L-His-Gly-OBzlNO₂ via the azide method. The linear octapeptide was obtained by coupling of the two tetrapeptide fragments: N-Boc-Gly-γ-OBu^t-L-Glu-Gly-Gly-ONp and L-His-Gly-L-His-Gly-OBzlNO₂. The cyclic peptide was purified to homogeneity by the method of countercurrent distribution. The product obtained was both ninhydrin negative and Pauli's reagent positive. Further confirmation of this material was obtained by the proper amino acid ratio of its acid hydrolysate and by the proton magnetic resonance spectrum in which the various kinds of protons of this peptide were accounted for. A detailed ¹³C- and ¹H-n.m.r. investigation was undertaken to determine the Zn(II)-binding ligands of the cyclo-octapeptide. The assignments for all the resonances were attempted by pH titration, by employing homonuclear decoupling experiments and by synthesis of cyclo-octapeptide containing specifically deuterated amino acids cyclo-(Gly-L-Glu-Gly-d₂-Gly-d₂-L-His-Gly-L-His-Gly). Titration results of Zn(II) bound form of the cyclic peptide showed the presence of a 1:1 complex. Upon Zn(II)-binding, the proton resonances were shifted downfield, the largest change being that of the histidine residues and more particularly C(2)-H protons. The chemical shifts induced on glutamic acid residue were also observed for Glu CH₂γ. In the case of ¹³C resonances, the maximum change in chemical shift was observed in the histidine residues and especially in the imidazole ring upon complexation. Two methylenes of the glutamic acid residue showed a large change in chemical shift upon ligating to the metal ion. The most significant observation was the deshielding effect of the Glu COO^- group. The results demonstrate that Zn(II) binds both the imidazoles of the two histidine residues and the carboxyl side chain of the glutamic acid residue of the designed cyclic octapeptide.     

A relaxed active site after exon ligation by the group I intron

During RNA maturation, the group I intron promotes two sequential phosphorotransfer reactions resulting in exon ligation and intron release. Here, we report the crystal structure of the intron in complex with spliced exons and two additional structures that examine the role of active-site metal ions during the second step of RNA splicing. These structures reveal a relaxed active site, in which direct metal coordination by the exons is lost after ligation, while other tertiary interactions are retained between the exon and the intron. Consistent with these structural observations, kinetic and thermodynamic measurements show that the scissile phosphate makes direct contact with metals in the ground state before exon ligation and in the transition state, but not after exon ligation. Despite no direct exonic interactions and even in the absence of the scissile phosphate, two metal ions remain bound within the active site. Together, these data suggest that release of the ligated exons from the intron is preceded by a change in substrate-metal coordination before tertiary hydrogen bonding contacts to the exons are broken.     

Metallothionein In Trace Metal Metabolism

While the unique function of metallothionein remains unknown, synthesis of the protein is induced by zinc, copper, cadmium and mercury. Zinc absorption, metabolism and transfer to apo-enzymes is promoted by zinc-thionein.