Eurocin,a New Fungal Defensin: STRUCTURE,LIPID BINDING,AND ITS MODE OF ACTION*

Antimicrobial peptides are a new class of antibiotics that are promising for pharmaceutical applications because they have retained efficacy throughout evolution. One class of antimicrobial peptides are the defensins, which have been found in different species. Here we describe a new fungal defensin, eurocin. Eurocin acts against a range of Gram-positive human pathogens but not against Gram-negative bacteria. Eurocin consists of 42 amino acids, forming a cysteine-stabilized α/β-fold. The thermal denaturation data point shows the disulfide bridges being responsible for the stability of the fold. Eurocin does not form pores in cell membranes at physiologically relevant concentrations; it does, however, lead to limited leakage of a fluorophore from small unilamellar vesicles. Eurocin interacts with detergent micelles, and it inhibits the synthesis of cell walls by binding equimolarly to the cell wall precursor lipid II.     

Estimation of Förster's distance between two ends of Dps protein from mycobacteria: distance heterogeneity as a function of oligomerization and DNA binding

Dps protein (DNA binding Protein from Starved Cells) from Mycobacterium smegmatis (Ms-Dps) is known to undergo an in vitro irreversible oligomeric transition from trimer to dodecamer. This transition helps the protein to provide for bimodal protection to the bacterial DNA from the free radical and Fenton mediated damages in the stationary state. The protein exists as a stable trimer, when purified from E. coli cells transformed with an over-expression plasmid. Both trimer as well as dodecamer are known to exhibit ferroxidation activity, thus removing toxic hydroxyl radicals in vivo, whereas iron accumulation and non-sequence specific DNA binding activity are found in dodecamer only. This seems to be aided by the positively charged long C-terminal tail of the protein. We used frequency domain phase-modulation fluorescence spectroscopy and Förster Resonance Energy Transfer (FRET) to monitor this oligomeric switch from a trimer to a dodecamer and to elucidate the structure of DNA–Dps dodecamer complex. As Ms-Dps is devoid of any Cysteine residues, a Serine is mutated to Cysteine (S169C) at a position adjacent to the putative DNA binding domain. This Cysteine is subsequently labeled with fluorescent probe and another probe is placed at the N-terminus, as crystal structure of the protein reveals several side-chain interactions between these two termini, and both are exposed towards the surface of the protein. Here, we report the Förster's distance distribution in the trimer and the dodecamer in the presence and absence of DNA. Through discrete lifetime analysis of the probes tagged at the respective regions in the macromolecule, coupled with Maximum Entropy Method (MEM) analysis, we show that the dodecamer, upon DNA binding shows conformational heterogeneity in overall structure, perhaps mediated by a non-specific DNA–protein interaction. On the other hand, the nature of DNA–Dps interaction is not known and several models exist in literature. We show here with the help of fluorescence anisotropy measurements of labeled DNA having different length and unlabeled native dodecameric protein that tandem occupation of DNA binding sites by a series of Dps molecules perhaps guide the tight packing of Dps over DNA backbone.     

Resonant neurons and bushcricket behaviour

The resonant properties of the intrinsic dynamics of single neurons could play a direct role in behaviour. One plausible role is in the recognition of temporal patterns, such as that seen in the auditory communication systems of Orthoptera. Recent behavioural data from bushcrickets suggests that this behaviour has interesting resonance properties, but the underlying mechanism is unknown. Here we show that a very simple and general model for neural resonance could directly account for the different behavioural responses of bushcrickets to different song patterns.     

Novel mutation in the fukutin gene in an Egyptian family with Fukuyama congenital muscular dystrophy and microcephaly

Fukuyama-type congenital muscular dystrophy (FCMD, MIM#253800) is an autosomal recessive disorder characterized by severe muscular dystrophy associated with brain malformations. FCMD is the second most common form of muscular dystrophy after Duchenne muscular dystrophy and one of the most common autosomal recessive diseases among the Japanese population, and yet few patients outside of Japan had been reported with this disorder. We report the first known Egyptian patient with FCMD, established by clinical features of generalized weakness, pseudohypertrophy of calf muscles, progressive joint contractures, severe scoliosis, elevated serum creatine kinase level, myopathic electrodiagnostic changes, brain MRI with cobblestone complex, and mutation in the fukutin gene. In addition, our patient displayed primary microcephaly, not previously reported associated with fukutin mutations. Our results expand the geographic and clinical spectrum of fukutin mutations.     

Critical issues for the proper diagnosis of Metachromatic Leukodystrophy

Metachromatic Leukodystrophy is a lysosomal storage disorder caused by Arylsulfatase A deficiency. Diagnosis is usually performed by measurement of enzymatic activity and/or characterization of the gene mutations. Here we describe a family case in which the determination of enzyme activity alone did not allow diagnosis of the pre-symptomatic sibling of the index case. Only combination of gene sequencing with thorough biochemical analysis allowed the correct diagnosis of the sibling, who was promptly directed to treatment.     

全数字化X线摄影联合MR动态增强检查诊断早期乳腺癌的临床价值研究

目的：分析早期乳腺癌的全数字X线摄影与MRI影像学表现,评价全数字X线摄影联合MRI检查在早期乳腺癌诊断中的临床价值。方法：回顾性分析2009年10月至2012年5月在我院经穿刺或手术病理证实为早期乳腺癌的42例患者的临床资料,术前均行数字X线及动态增强MR检查,比较两种方法单独使用和联合使用的诊断乳腺癌的准确率。结果：全数字化X线摄片诊断早期乳腺癌的准确率为69．0％（29／42）,动态增强MR检查为95．2％（40／42）,两者比较差异有统计学意义（P〈0．05）;两者联合使用诊断早期乳腺癌的准确率为97．6％（41／42）。结论：动态增强MR检查对早期乳腺癌的诊断价值明显优于全数字X线摄影,但后者对微小钙化显示较好,两者联合可提高诊断正确率,尤其对多腺体型和致密型乳腺的早期乳腺癌的检出具有重要的价值。     

Delineating biased ligand efficacy at 7TM receptors from an experimental perspective

During the last 10 years, the concept of “biased agonism” also called “functional selectivity” swamped the pharmacology of 7 transmembrane receptors and paved the way for developing signaling pathway-selective drugs with increased efficacy and less adverse effects. Initially thought to select the activation of only a subset of the signaling pathways by the reference agonist, bias ligands revealed higher complexity as they have been shown to stabilize variable receptor conformations that associate with distinct signaling events from the reference. Today, one major challenge relies on the in vitro determination of the bias and classification of these ligands, as a prerequisite for future in vivo and clinical translation. In this review, current experimental considerations for the bias evaluation related to choice of the cellular model, of the signaling pathway as well as of the assays are presented and discussed.     

Some Photosystem II properties depending on the D1 protein variants in Thermosynechococcus elongatus

Cyanobacteria have multiple psbA genes encoding PsbA, the D1 reaction center protein of the Photosystem II complex which bears together with PsbD, the D2 protein, most of the cofactors involved in electron transfer reactions. The thermophilic cyanobacterium Thermosynechococcus elongatus has three psbA genes differently expressed depending on the environmental conditions. Among the 344 residues constituting each of the 3 possible PsbA variants there are 21 substitutions between PsbA1 and PsbA3, 31 between PsbA1 and PsbA2 and 27 between PsbA2 and PsbA3. In this review, we summarize the changes already identified in the properties of the redox cofactors depending on the D1 variant constituting Photosystem II in T. elongatus. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: Keys to Produce Clean Energy.     

Resonance-based oscillations could describe human gait mechanics under various loading conditions

The oscillatory behavior of the center of mass (CoM) and the corresponding ground reaction force (GRF) of human gait for various gait speeds can be accurately described in terms of resonance using a spring–mass bipedal model. Resonance is a mechanical phenomenon that reflects the maximum responsiveness and energetic efficiency of a system. To use resonance to describe human gait, we need to investigate whether resonant mechanics is a common property under multiple walking conditions. Body mass and leg stiffness are determinants of resonance; thus, in this study, we investigated the following questions: (1) whether the estimated leg stiffness increased with inertia, (2) whether a resonance-based CoM oscillation could be sustained during a change in the stiffness, and (3) whether these relationships were consistently observed for different walking speeds. Seven healthy young subjects participated in over-ground walking trials at three different gait speeds with and without a 25-kg backpack. We measured the GRFs and the joint kinematics using three force platforms and a motion capture system. The leg stiffness was incorporated using a stiffness parameter in a compliant bipedal model that best fitted the empirical GRF data. The results showed that the leg stiffness increased with the load such that the resonance-based oscillatory behavior of the CoM was maintained for a given gait speed. The results imply that the resonance-based oscillation of the CoM is a consistent gait property and that resonant mechanics may be useful for modeling human gait.