Multimeric bivalent immunogens from recombinant tetanus toxin H<Subscript>C</Subscript> fragment,synthetic hexasaccharides,and a glycopeptide adjuvant

Using recombinant tetanus toxin H_C fragment (rTT-H_C) as carrier, we prepared multimeric bivalent immunogens featuring the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Ogawa, in combination with either the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Inaba, or a synthetic disaccharide tetrapeptide peptidoglycan fragment as adjuvant. The conjugation reaction was effected by squaric acid chemistry and monitored in virtually real time by SELDI-TOF MS. In this way, we could prepare well-defined immunogens with predictable carbohydrate–carrier ratio, whose molecular mass and the amount of each saccharide attached could be independently determined. The ability to prepare such neoglycoconjugates opens unprecedented possibilities for preparation of conjugate vaccines for bacterial diseases from synthetic carbohydrates.     

Differences in erythropoiesis in normal chicken and quail embryos

Summary Using antibodies against the fetal and adult forms of - and -globin, it has been shown that erythropoiesis in the para-aortic foci (PAF) constitutes a major species-specific difference between chicken and quail embryos. In quail embryos, para-aortic foci are rare, small and rather heterogeneous with regard to their erythropoietic and haemopoietic cell composition. In contrast, the PAFs in chicken embryos are abundant and consist of large numbers of erythropoietic cells.In both species a time difference (approximately 1 day) is observed between the first expression of the fetal - and -globin and the adult - and -globin in erythropoietic cells. Adult erythropoiesis in both species can be detected first in the stalk of the yolk sac; this is similar to the situation in mammalian and amphibian species. From this time onward the number of circulating adult erythrocytes increases steadily. Whereas in chicken, large intraembryonic foci that can serve as sources for these adult cells arise concomitantly, no such foci can be detected in quail embryos, suggesting that the quail yolk sac is a major source for these adult red blood cells.     

Reaction of cytochrome c2 with photosynthetic reaction centers from Rhodopseudomonas viridis.

The reactions of Rhodopseudomonas viridis cytochrome c2 and horse cytochrome c with Rps. viridis photosynthetic reaction centers were studied by using both single- and double-flash excitation. Single-flash excitation of the reaction centers resulted in rapid photooxidation of cytochrome c-556 in the cytochrome subunit of the reaction center. The photooxidized cytochrome c-556 was subsequently reduced by electron transfer from ferrocytochrome c2 present in the solution. The rate constant for this reaction had a hyperbolic dependence on the concentration of cytochrome c2, consistent with the formation of a complex between cytochrome c2 and the reaction center. The dissociation constant of the complex was estimated to be 30 microM, and the rate of electron transfer within the 1:1 complex was 270 s-1. Double-flash experiments revealed that ferricytochrome c2 dissociated from the reaction center with a rate constant of greater than 100 s-1 and allowed another molecule of ferrocytochrome c2 to react. When both cytochrome c-556 and cytochrome c-559 were photooxidized with a double flash, the rate constant for reduction of both components was the same as that observed for cytochrome c-556 alone. The observed rate constant decreased by a factor of 14 as the ionic strength was increased from 5 mM to 1 M, indicating that electrostatic interactions contributed to binding. Molecular modeling studies revealed a possible cytochrome c2 binding site on the cytochrome subunit of the reaction center involving the negatively charged residues Glu-93, Glu-85, Glu-79, and Glu-67 which surround the heme crevice of cytochrome c-554.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of shear on morphology,viability and metabolic activity of succinic acid-producing Actinobacillus succinogenes biofilms

Two custom-designed bioreactors were used to evaluate the effect of shear on biofilms of a succinic acid producer, Actinobacillus succinogenes. The first bioreactor allowed for in situ removal of small biofilm samples used for microscopic imaging. The second bioreactor allowed for complete removal of all biofilm and was used to analyse biofilm composition and productivity. The smooth, low porosity biofilms obtained under high shear conditions had an average cell viability of 79% compared to 57% at the lowest shear used. The maximum cell-based succinic acid productivity for high shear biofilm was 2.4 g g⁻¹DCW h⁻¹ compared to the 0.8 g g⁻¹DCW h⁻¹ of the low shear biofilm. Furthermore, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays confirmed higher cell metabolic activities for high shear developed biofilm compared to biofilm developed at low shear conditions. Results clearly indicated that high shear biofilm cultivation has beneficial morphological, viability, and cell-based productivity characteristics.

     

Life cycle assessment of emerging technologies at the lab scale: The case of nanowire‐based solar cells

Nanomaterials are expected to play an important role in the development of sustainable products. The use of nanomaterials in solar cells has the potential to increase their conversion efficiency. In this study, we performed a life cycle assessment (LCA) for an emerging nanowire‐based solar technology. Two lab‐scale manufacturing routes for the production of nanowire‐based solar cells have been compared—the direct growth of GaInP nanowires on silicon substrate and the growth of InP nanowires on native substrate, peel off, and transfer to silicon substrate. The analysis revealed critical raw materials and processes of the current lab‐scale manufacturing routes such as the use of trifluoromethane (CHF₃), gold, and an InP wafer and a stamp, which are used and discarded. The environmental performance of the two production routes under different scenarios has been assessed. The scenarios include the use of an alternative process to reduce the gold requirements—electroplating instead of metallization, recovery of gold, and reuse of the InP wafer and the stamp. A number of suggestions, based on the LCA results—including minimization of the use of gold and further exploration for upscaling of the electroplating process, the increase in the lifetimes of the wafer and the stamp, and the use of fluorine‐free etching materials—have been communicated to the researchers in order to improve the environmental performance of the technology. Finally, the usefulness and limitations of lab‐scale LCA as a tool to guide the sustainable development of emerging technologies are discussed.     

Ex ante life cycle assessment of GaAs/Si nanowire–based tandem solar cells: a benchmark for industrialization

The International Journal of Life Cycle Assessment - The goal of this study is to perform an ex-ante life cycle assessment (LCA) of the emerging gallium-arsenide nanowire tandem solar cells on...     

Chemoenzymatic synthesis of immunogenic meningococcal group C polysialic acid-tetanus Hc fragment glycoconjugates

Vaccination with meningococcal glycoconjugate vaccines has decreased the incidence of invasive meningitis worldwide. These vaccines contain purified capsular polysaccharides attached to a carrier protein. Because of derivatization chemistries used in the process, conjugation of polysaccharide to protein often results in heterogeneous mixtures. Well-defined vaccines are needed to determine the relationship between vaccine structure and generated immune response. Here, we describe efforts to produce well-defined vaccine candidates by chemoenzymatic synthesis. Chemically synthesized lactosides were substrates for recombinant sialyltransferase enzymes from Camplyobacter jejuni and Neisseria meningitidis serogroup C. These resulting oligosialic acids have the same α(2-9) sialic acid repeat structure as Neisseria polysaccharide capsule with the addition of a conjugatable azide aglycon. The degree of polymerization (DP) of carbohydrate products was controlled by inclusion of the inhibitor CMP-9-deoxy-NeuNAc. Polymers with estimated DP?<?47 (median DP 25) and DP?<?100 (median DP 51) were produced. The receptor binding domain of the tetanus toxin protein (TetHc) was coupled as a carrier to the enzymatically synthesized oligosialic acids. Recombinant TetHc was derivatized with an alkyne squarate. Protein modification sites were determined by trypsin proteolysis followed by LC/MS-MS^E analysis of peptides. Oligosialic acid azides were conjugated to modified TetHc via click chemistry. These chemoenzymatically prepared glycoconjugates were reactive in immunoassays with specific antibodies against either group C polysaccharide or TetHc. Sera of mice immunized with oligosialic acid-TetHc glycoconjugates contained much greater levels of polysaccharide-reactive IgG than the sera of control mice receiving unconjugated oligosialic acids. There was no apparent difference between glycoconjugates containing oligosaccharides of DP?<?47 and DP?<?100. These results suggest that chemoenzymatic synthesis may provide a viable method for making defined meningococcal vaccine candidates.     

Integrating HIV Care into Primary Care Services: Quantifying Progress of an Intervention in South Africa

Background

Integration of human immunodeficiency virus (HIV) care into primary care services is one strategy proposed to achieve universal access to antiretroviral treatment (ART) for HIV-positive patients in high burden countries. There is a need for controlled studies of programmes to integrate HIV care with details of the services being integrated.

Methods

A semi-quantitative questionnaire was developed in consultation with clinic staff, tested for internal consistency using Cronbach''s alpha coefficients and checked for inter-observer reliability. It was used to conduct four assessments of the integration of HIV care into referring primary care clinics (mainstreaming HIV) and into the work of all nurses within ART clinics (internal integration) and the integration of pre-ART and ART care during the Streamlining Tasks and Roles to Expand Treatment and Care for HIV (STRETCH) trial in South Africa. Mean total integration and four component integration scores at intervention and control clinics were compared using one way analysis of variance (ANOVA). Repeated measures ANOVA was used to analyse changes in scores during the trial.

Results

Cronbach''s alpha coefficients for total integration, pre-ART and ART integration and mainstreaming HIV and internal integration scores showed good internal consistency. Mean total integration, mainstreaming HIV and ART integration scores increased significantly at intervention clinics by the third assessment. Mean pre-ART integration scores were almost maximal at the first assessment and showed no further change. There was no change in mean internal integration score.

Conclusion

The questionnaire developed in this study is a valid tool with potential for monitoring integration of HIV care in other settings. The STRETCH trial interventions resulted in increased integration of HIV care, particularly ART care, by providing HIV care at referring primary care clinics, but had no effect on integrating HIV care into the work of all nurses with the ART clinic.