Conformational analysis and molecular dynamics simulations of maltose

Constrained conformational energy minimizations have been used to calculate an adiabatic (Φ, ψ) potential energy surface for the disaccharide β-maltose. The inclusion of molecular flexibility in the conformational energy analysis of the disaccharide was found to significantly lower the barriers to conformational transitions, as has been observed previously for other systems. Several low energy wells were identified on the adiabatic surface which differ in energy by small amounts and with low absolute barriers separating them, indicating the possibility of a non-negligible equilibrium population distribution in each well. If such a distribution of conformations existed in the physical system, the conformation observed by NMR NOE measurements would thus be a “virtual” conformation. Molecular dynamics simulations of the motions of this molecule in vacuum were also conducted and indicate that the rate of relaxation of the molecule to the adiabatic surface may be slower than the typical timescale of conformational fluctuations. This effect is apparently due to an unphysical persistence of hydrogen bond patterns in vacuum which does not occur in aqueous solution. Trajectories undergoing transitions between wells were calculated and the effects of such conformational transitions upon the ensemble mean structure, such as might be observed in an NMR experiment, were demonstrated.     

The use of hollow fiber cross-flow microfiltration in bioaccumulation and continuous removal of heavy metals from solution by Saccharomyces cerevisiae

Cross-flow microfiltration was shown to retain Saccharomyces cerevisiae biomass utilized for heavy metal bioaccumulation. The passage of metal-laden influent through a series of sequential bioaccumulation systems allowed for further reductions in the levels of copper, cadmium, and cobalt in the final effluent than that afforded by a single bioaccumulation process. Serial bioaccumulation systems also allowed for partial separation of metals from dual metal influents. More than one elemental metal cation could be accumulated simultaneously and in greater quantities than when a single metal was present in the effluent (Cu(2+) 0.43 mmol, Cu(2+) + Cd(2+) 0.67 mmol, and Cu(2+) + Co(2+) 0.83 mmol/g yeast dry mass when the initial concentration of each of the metal species was 0.2 mmol.L(-1)). Co-accumulation of two different metal cations allowed higher total levels of bioaccumulation than found with a single metal. The flux rate was 2.9 x 10(2) L.h(-2)mum(-2) using a polypropylene microfiltration membrane (0.1 mum pore size) at 25 degrees C. (c) 1994 John Wiley & Sons, Inc.     

Molecular mapping of the Rf 3 fertility restoration gene to facilitate its utilization in breeding confection sunflower

The inheritance of a previously identified dominant Rf gene in the confection sunflower line RHA 280 has been determined and designated as Rf ₃ . This study reports the mapping of the Rf ₃ locus using an F2 population of 227 individuals derived from CMS HA 89-3149 × RHA 280. Bulked segregant analysis with 624 pairs of simple sequence repeat (SSR) primers and sequence tagged site (STS) primers identified two polymorphic SSR markers each of linkage groups (LGs) 7 and 11 from a previous map. Results on 90 F2 individuals with 42 polymorphic markers of LGs 7 and 11 indicated that the Rf ₃ gene was linked with eight markers on LG 7, including five SSR markers (ORS328, ORS331, ORS928, ORS966, and ORS1092) and three expressed sequence tag (EST)-SSR markers (HT619-1, HT619-2, and HT1013). Further analysis of the total F2 population of 227 individuals identified a co-dominant marker, ORS328, linked to Rf ₃ at a genetic distance of 0.7 cM on one side, and a female-dominant marker HT1013 at 12.6 cM proximal to Rf ₃ on the other side; a genetic distance of 47.1 cM for LG 7 was covered. This is the first report of an Rf gene from the confection sunflower. The closely linked marker to Rf ₃ will facilitate marker-assisted selection, and provide a basis for cloning of this gene.     

A reliable method for assessing rotational power

Rotational core training is said to be beneficial for rotational power athletes. Currently, there has been no method proposed for the reliable assessment of rotational power. Therefore, our purpose was to determine the test-retest reliability of kinetic and kinematic rotational characteristics of a pulley system when performing a rotational exercise of the axial skeleton in the transverse plane to find out if this would be a reliable tool for evaluating rotational power. Healthy, college-aged men (n = 8) and women (n = 15) reported for 3 testing sessions. The participants were seated on a box, and they held the handle with both arms extended in front of their body, starting their motion with their torso rotated toward the machine. All the participants rotated their torso forcefully until they reached 180° of rotation, and they then slowly returned to the starting position, 3 times per trial, with 3 loads: 9% body weight (BW), 12% BW, and 15% BW. The repetition with the greatest power for each trial for each load was analyzed. The mean peak power repetition (watts) for all the subjects was 20.09 ± 7.16 (9% BW), 26.17 ± 8.6 (12% BW), and 30.74 ± 11.022 (15% BW) in the first training session and 22.3 ± 8.087 (9% BW), 28.7 ± 11.295 (12% BW), and 33.52 ± 12.965 (15% BW) in the second training session with intraclass correlation coefficients of 0.97 (9%BW), 0.94 (12%BW), and 0.95 (15%BW). When the participants were separated by sex, there were no significant differences between groups. Based on these results, it was found that a pulley system and an external dynamometer can be used together as a reliable research tool to assess rotational power.     

Expression of the Receptor Tyrosine Kinase EphB2 on Dendritic Cells Is Modulated by Toll-Like Receptor Ligation but Is Not Required for T Cell Activation

The Eph receptor tyrosine kinases interact with their ephrin ligands on adjacent cells to facilitate contact-dependent cell communication. Ephrin B ligands are expressed on T cells and have been suggested to act as co-stimulatory molecules during T cell activation. There are no detailed reports of the expression and modulation of EphB receptors on dendritic cells, the main antigen presenting cells that interact with T cells. Here we show that mouse splenic dendritic cells (DC) and bone-marrow derived DCs (BMDC) express EphB2, a member of the EphB family. EphB2 expression is modulated by ligation of TLR4 and TLR9 and also by interaction with ephrin B ligands. Co-localization of EphB2 with MHC-II is also consistent with a potential role in T cell activation. However, BMDCs derived from EphB2 deficient mice were able to present antigen in the context of MHC-II and produce T cell activating cytokines to the same extent as intact DCs. Collectively our data suggest that EphB2 may contribute to DC responses, but that EphB2 is not required for T cell activation. This result may have arisen because DCs express other members of the EphB receptor family, EphB3, EphB4 and EphB6, all of which can interact with ephrin B ligands, or because EphB2 may be playing a role in another aspect of DC biology such as migration.     

Cytogenetic darkroom magic: now you see them, now you don''t.

Customary procedures used to determine chromosomal inheritance do not disclose many of the chromosomal polymorphisms known to be present, resulting in uninformative families. The sequential printing of individual chromosomes presented here is a technique that has increased the number of informative families in our studies. This technique has revealed previously unseen heritable chromosome differences and allowed the designation of parental origin.     

Light capture and pigment diversity in marine and freshwater cryptophytes

Phenotypic traits associated with light capture and phylogenetic relationships were characterized in 34 strains of diversely pigmented marine and freshwater cryptophytes. Nuclear SSU and partial LSU rDNA sequence data from 33 of these strains plus an additional 66 strains produced a concatenated rooted maximum likelihood tree that classified the strains into 7 distinct clades. Molecular and phenotypic data together support: (i) the reclassification of Cryptomonas irregularis NIES 698 to the genus Rhodomonas, (ii) revision of phycobiliprotein (PBP) diversity within the genus Hemiselmis to include cryptophyte phycocyanin (Cr‐PC) 569, (iii) the inclusion of previously unidentified strain CCMP 2293 into the genus Falcomonas, even though it contains cryptophyte phycoerythrin 545 (Cr‐PE 545), and (iv) the inclusion of previously unidentified strain CCMP 3175, which contains Cr‐PE 545, in a clade with PC‐containing Chroomonas species. A discriminant analysis‐based model of group membership correctly predicted 70.6% of the clades using three traits: PBP concentration · cell^?1, the wavelength of PBP maximal absorption, and habitat. Non‐PBP pigments (alloxanthin, chl‐a, chl‐c₂, α‐carotene) did not contribute significantly to group classification, indicating the potential plasticity of these pigments and the evolutionary conservation of the PBPs. Pigment data showed evidence of trade‐offs in investments in PBPs vs. chlorophylls (a +c₂).     

Enhancing macroautophagy protects against ischemia/reperfusion injury in cardiac myocytes

Cardiac myocytes undergo programmed cell death as a result of ischemia/reperfusion (I/R). One feature of I/R injury is the increased presence of autophagosomes. However, to date it is not known whether macroautophagy functions as a protective pathway, contributes to programmed cell death, or is an irrelevant event during cardiac I/R injury. We employed simulated I/R of cardiac HL-1 cells as an in vitro model of I/R injury to the heart. To assess macroautophagy, we quantified autophagosome generation and degradation (autophagic flux), as determined by steady-state levels of autophagosomes in relation to lysosomal inhibitor-mediated accumulation of autophagosomes. We found that I/R impaired both formation and downstream lysosomal degradation of autophagosomes. Overexpression of Beclin1 enhanced autophagic flux following I/R and significantly reduced activation of pro-apoptotic Bax, whereas RNA interference knockdown of Beclin1 increased Bax activation. Bcl-2 and Bcl-x(L) were protective against I/R injury, and expression of a Beclin1 Bcl-2/-x(L) binding domain mutant resulted in decreased autophagic flux and did not protect against I/R injury. Overexpression of Atg5, a component of the autophagosomal machinery downstream of Beclin1, did not affect cellular injury, whereas expression of a dominant negative mutant of Atg5 increased cellular injury. These results demonstrate that autophagic flux is impaired at the level of both induction and degradation and that enhancing autophagy constitutes a powerful and previously uncharacterized protective mechanism against I/R injury to the heart cell.