Bragg-Scattered Surface Plasmon Microscopy: Theoretical Study

We present a new approach to surface plasmon microscopy with high refractive index sensitivity and spatial resolution that is not limited by the propagation length of surface plasmons. It is based on a nanostructured metallic sensor surface supporting Bragg-scattered surface plasmons. We show that these non-propagating surface plasmon modes are excellently suited for spatially resolved observations of refractive index variations on the sensor surface owing to their highly confined field profile perpendicular to as well as parallel to the metal interface. The presented theoretical study reveals that this approach enables reaching similar refractive index sensitivity as regular surface plasmon resonance (SPR) microscopy and offers the advantage of improved spatial resolution when observing dielectric features with lateral size <10???m for the wavelength around 800?nm and gold as the SPR-active metal. This paper demonstrates the potential of Bragg-scattered surface plasmon microscopy for high-throughput SPR biosensing with high-density microarrays.     

QTL analysis of early-season cold tolerance in sorghum

Cool temperatures during the early-growing season are a major limitation to growing sorghum [Sorghum bicolor (L.) Moench] in temperate areas. Several landraces from China have been found to exhibit higher emergence and greater seedling vigor under cool conditions than most breeding lines currently available, but tend to lack desirable agronomic characteristics. The introgression of desirable genes from Chinese landraces into elite lines could be expedited by marker-assisted selection. Using a population of 153 RI lines, developed from a cross between Chinese landrace ‘Shan Qui Red,’ (SQR, cold-tolerant) and SRN39 (cold-sensitive), QTL associated with early-season performance under both cold and optimal conditions were identified by single marker analysis, simple interval mapping (SIM), and composite interval mapping (CIM). Germination was observed under controlled conditions, and other traits were measured in field plantings. Two QTL for germination were identified: one on linkage group SBI-03a, derived from SRN39, was significant under cold and optimal temperatures. The other, on group SBI-07b, showed greater significance under cold temperatures and was contributed by SQR. A region of group SBI-01a, derived from SQR, showed strong associations with seedling emergence and seedling vigor scores under early and late field plantings. A QTL for both early and late emergence was identified by CIM on SBI-02 which favored the SRN39 allele. SIM identified a QTL for early vigor on SBI-04 favoring the SQR genotype. Further studies are needed to validate the effects of these QTL, but they represent the first step in development of a marker-assisted breeding effort to improve early-season performance in sorghum.     

Trypanosoma cruzi: Induction of benznidazole resistance in vivo and its modulation by in vitro culturing and mice infection

Through a continuous in vivo drug pressure protocol, using mice as experimental model, we induced benznidazole resistance in Trypanosoma cruzi stocks. Full resistance was obtained for four out of five T. cruzi stocks analyzed. However, the number of benznidazole doses (40–180), as well as the time (4–18 months) necessary to induce resistance varied among the different T. cruzi stocks. The resistance phenotype remained stable after T. cruzi stocks has been maintained by 12 passages in mice (six months) and in acellular culture for the same time. However, the maintenance of resistant parasite for 12 months in acellular culture induces a reduction in its level of benznidazole resistance, while no alteration was detected in parasite maintained for the same time in mice. The data showed the stability of the resistance acquired by drug pressure, but suggest the possibility of reversible changes in the resistance levels after maintenance for long time in acellular culture.     

Cytokine release and expression induced by OmpA proteins from the Gram-negative anaerobes, Porphyromonas asaccharolytica and Bacteroides fragilis

OmpA proteins from Gram-negative anaerobes Porphyromonas asaccharolytica and Bacteroides fragilis induced release and expression of IL-1alpha, tumor necrosis factor (TNF)-alpha, IFN-gamma, IL-6, and IL-10 from murine splenocytes in vitro in a dose-dependent fashion. The release of the cytokines induced by B. fragilis Bf-OmpA was at much lower levels compared with P. asaccharolytica Omp-PA; Bf-OmpA did not induce release of IL-10. Omp-PA and Bf-OmpA were able to upregulate mRNA expression of the tested cytokines. The results obtained with refolded Bf-OmpA were similar to those with native Bf-OmpA. The data presented in this research demonstrate for the first time that Omps from anaerobic bacteria can induce the release of cytokines, suggesting that Omp-PA and Bf-OmpA may play important roles in the pathogenic processes of these bacteria.     

Electronic wiring of a multi-redox site membrane protein in a biomimetic surface architecture

Bioelectronic coupling of multi-redox-site membrane proteins was accomplished with cytochrome c oxidase (CcO) as an example. A biomimetic membrane system was used for the oriented immobilization of the CcO oxidase on a metal electrode. When the protein is immobilized with the CcO binding side directed toward the electrode and reconstituted in situ into a lipid bilayer, it is addressable by direct electron transfer to the redox centers. Electron transfer to the enzyme via the spacer, referred to as electronic wiring, shows an exceptionally high rate constant. This allows a kinetic analysis of all four consecutive electron transfer steps within the enzyme to be carried out. Electron transfer followed by rapid scan cyclic voltametry in combination with surface-enhanced resonance Raman spectroscopy provides mechanistic and structural information about the heme centers. Probing the enzyme under turnover conditions showed mechanistic insights into proton translocation coupled to electron transfer. This bioelectronic approach opens a new field of activity to investigate complex processes in a wide variety of membrane proteins.     

Gait adaptation in ACL deficient patients before and after anterior cruciate ligament reconstruction surgery.

The objective of this study is to determine how kinematical parameters and electromyography data of selected muscles may change as a result of anterior cruciate ligament (ACL) deficiency and following ACL reconstruction. The study was conducted on 25 anterior cruciate ligament deficient subjects prior to and 6 weeks, 4 months, 8 months and 12 months following ACL reconstructive surgery using the bone-patellar tendon-bone technique. Gait analysis was performed by applying the zebris three-dimensional ultrasound-based system with surface electromyograph (zebris). Kinematic data were recorded for the lower limb. The muscles surveyed include vastus lateralis and medialis, biceps femoris and adductor longus. The results obtained from the injured subjects were compared with those of 51 individuals without any ACL damage whatsoever. Acute ACL deficient patients exhibited a quadriceps avoidance pattern prior to and 6 weeks following surgery. No quadriceps avoidance phenomenon develops in chronic ACL deficient patients. In operated individuals, tempo-spatial parameters and the knee angle regained a normal pattern for the ACL-deficient limb during gait as early as 4 months following surgery. However, the relative ACL movement parameter, which describes the tibial translation into the direction of ACL, and the EMG traces show no significant statistical difference compared with the same values of the healthy control group just 8 months following surgery. The analysis of spatial-temporal parameters and EMG traces show that the development of a quadriceps avoidance pattern is less common than previously reported. These data suggest that anterior cruciate ligament deficiency and reconstruction produce considerable changes in the lower extremity gait pattern. The results suggest that gait parameters tend to shift towards a normal value pattern; and the re-establishment of pre-injury gait patterns-including the normal biphase of muscles-takes at least 8 months to occur.     

Branched activation- and catalysis-specific pathways for electron relay to the manganese/iron cofactor in ribonucleotide reductase from Chlamydia trachomatis

A conventional class I (subclass a or b) ribonucleotide reductase (RNR) employs a tyrosyl radical (Y (*)) in its R2 subunit for reversible generation of a 3'-hydrogen-abstracting cysteine radical in its R1 subunit by proton-coupled electron transfer (PCET) through a network of aromatic amino acids spanning the two subunits. The class Ic RNR from the human pathogen Chlamydia trachomatis ( Ct) uses a Mn (IV)/Fe (III) cofactor (specifically, the Mn (IV) ion) in place of the Y (*) for radical initiation. Ct R2 is activated when its Mn (II)/Fe (II) form reacts with O 2 to generate a Mn (IV)/Fe (IV) intermediate, which decays by reduction of the Fe (IV) site to the active Mn (IV)/Fe (III) state. Here we show that the reduction step in this sequence is mediated by residue Y222. Substitution of Y222 with F retards the intrinsic decay of the Mn (IV)/Fe (IV) intermediate by approximately 10-fold and diminishes the ability of ascorbate to accelerate the decay by approximately 65-fold but has no detectable effect on the catalytic activity of the Mn (IV)/Fe (III)-R2 product. By contrast, substitution of Y338, the cognate of the subunit interfacial R2 residue in the R1 <--> R2 PCET pathway of the conventional class I RNRs [Y356 in Escherichia coli ( Ec) R2], has almost no effect on decay of the Mn (IV)/Fe (IV) intermediate but abolishes catalytic activity. Substitution of W51, the Ct R2 cognate of the cofactor-proximal R1 <--> R2 PCET pathway residue in the conventional class I RNRs (W48 in Ec R2), both retards reduction of the Mn (IV)/Fe (IV) intermediate and abolishes catalytic activity. These observations imply that Ct R2 has evolved branched pathways for electron relay to the cofactor during activation and catalysis. Other R2s predicted also to employ the Mn/Fe cofactor have Y or W (also competent for electron relay) aligning with Y222 of Ct R2. By contrast, many R2s known or expected to use the conventional Y (*)-based system have redox-inactive L or F residues at this position. Thus, the presence of branched activation- and catalysis-specific electron relay pathways may be functionally important uniquely in the Mn/Fe-dependent class Ic R2s.     

New skull of Lesothosaurus (Dinosauria: Ornithischia) from the Upper Elliot Formation (Lower Jurassic) of southern Africa

A new ornithischian skull from the Elliot Formation of southern Africa is described. The specimen is compared in detail with the fabrosaurid Lesothosaurus diagnosticus. It actually shares many characters with specimens of the syntypes of this species or specimens referred to it. It is nevertheless not identical to any of these specimens and it is, moreover, remarkably larger than them. The possibility of attributing this specimen to a so far undescribed ‘large fabrosaur’ from the same formation is discussed. It is concluded that the specimen in question in this paper, while being ascribable to the genus Lesothosaurus, cannot be determined to a specific level until the existence of two fabrosaurid species in the ‘Stormberg Group’ is demonstrated and their range of morphological and size variation is properly appraised.