Histotoxic clostridia produce collagenases responsible for extensive tissue destruction in gas gangrene. The C-terminal collagen-binding domain (CBD) of these enzymes is the minimal segment required to bind to collagen fibril. Collagen binding efficiency of CBD is more pronounced in the presence of Ca Histotoxic clostridia produce collagenases that degrade collagen in connective tissue. Although the enzyme is assumed to be a causative agent for diseases like gas gangrene (1), it is beneficial to remove dead tissue from ulcers or burns and for nonsurgical treatment of Dupuytren's disease (2, 3). For collagenases to hydrolyze tissue collagen, the enzymes must 1) anchor themselves onto an insoluble collagen fibril, which is a staggered array of tropocollagen and then 2) isolate a single triple helical molecule from the bundle and finally 3) unwind the triple helix to expose a scissile peptide bond. Clostridium histolyticum produces two classes of collagenases, which contain a catalytic domain belonging to the family M9B, followed by one or two copies of polycystic kidney disease domains and one or two copies of collagen-binding domains (CBD) 2 (4). Each CBD spans ϳ120 amino acid residues and binds specifically to insoluble collagen. CBD also binds to collagenous peptides with triple helical conformation but not to collagenous peptides that lack triple helix or to gelatin (denatured collagen), suggesting that the CBD-collagen interaction is conformation-specific (4, 5). Calcium ions enhance the binding at physiological concentration, and x-ray crystal structures of CBD have been solved in the presence and absence of calcium (6).Since collagen fibrils constitute a major part of the extracellular matrix, bioactive molecules can be anchored with CBD for their prolonged effect. Nishi et al. (7) have demonstrated that growth factors fused to CBD remained at the sites of injection much longer than growth factors alone to induce extended cell proliferation. In order to gain an insight into the anchoring mechanism of CBD, we attempted to co-crystallize CBD and collagenous peptide without success. Also to better address the role of CBD in fibril disruption and transition states from insoluble substrate, solution studies of CBD with the triple helical collagenous peptide became necessary.NMR titration methods were utilized to identify the collagen binding pocket on CBD. Since it has been shown that most peptidases bind to their substrate in one direction at their catalytic center (8, 9), there could be only one direction for the collagen triple helices at the binding site of CBD. On the other hand, CBD might allow bidirectional binding, since it is independent of the catalytic domain. To identify the binding direction, three different NMR titrations were performed with spinlabeled analogues of tropocollagen, where a nitroxide spin label 2,2,5,5-tetramethyl-L-pyrrolidinyloxy (PROXYL) was attached to either the N or C terminus of the collagenous peptide. The nitroxide moiety with an unpaired electron can cause enhancement in pa...

The low-temperature crystal structure of Fe1.13Te, which exhibits an anomalous two-step magnetic transition, was clarified by the systematic x-ray diffraction measurements. It was found that two-step structural phase transition, tetragonal-orthorhombic-monoclinic, occurred correspondingly to the two-step magnetic transition. The detailed analysis of the profile at 5 K indicated the coexistence of the minor orthorhombic area inside the major monoclinic lattice, which could explain the lower-shift (suppression) of the antiferromagnetic transition temperature in Fe1.13Te and suggest a possibility of superconductivity at the domain boundary.

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We screened the antihyperlipidemic effects of seven edible plants by evaluation of the triglyceride (TG) and cholesterol profiles secreted from HepG2 cells. We found that the water- and ethanol-extracts of Brasenia schreberi at 100 μg/ml exhibited strong inhibitory activities against TG and cholesterol secretions from HepG2 cells stimulated with sodium oleate. Real-time RT-PCR analysis demonstrated that ethanol extract of B. schreberi (BSET) attenuated the expression of the sterol regulatory element binding protein-1c and -2, fatty acid synthase and HMG CoA synthase-1 genes, which are involved in lipid synthesis in hepatocyte/hepatoma cells. Furthermore, we studied the action of BSET on adipose tissue accumulation and serum parameters in mice fed a high-fat diet (HFD). BSET suppressed mesenteric and epididymal adipose tissue accumulation and normalized serum TG and glucose, but not cholesterol levels in HFD-fed mice.

in order to visualize restricted diffusion, the present study developed a novel method called 'apparent diffusion coefficient (ADC) subtraction method (ASM)' and compared it with diffusion kurtosis imaging (DKI). The diffusion-weighted images of physiological saline, in addtion to bio-phatoms of low cell density and the highest cell density were obtained using two sequences with different effective diffusion times. Then, the calculated ADC values were subtracted. The mean values and standard deviations (SD) of the ADC values of physiological saline, low cell density and the highest cell density phantoms were 2.95±0.08x10-3 , 1.90±0.35x10-3 and 0.79±0.05x10-3 mm 2 /sec, respectively. The mean kurtosis values and SD of DKI were 0.04±0.01, 0.44±0.13 and 1.27±0.03, respectively. The ASM and SD values were 0.25±0.20x10 4 , 0.51±0.41x10 4 and 4.80±4.51x10 4 (sec/mm 2) 2 , respectively. Using bio-phantoms, the present study demonstrated that DKI exhibits restricted diffusion in the extracellular space. Similarly, ASM may reflect the extent of restricted diffusion in the extracellular space.