Solar energy conversion efficiencies in photosynthesis: Minimizing the chlorophyll antennae to maximize efficiency

The theoretical maxima of solar energy conversion efficiencies and productivities in oxygenic photosynthesis are evaluated. These are contrasted with actual measurements in a variety of photosynthetic organisms, including green microalgae, cyanobacteria, C4 and C3 plants. Minimizing, or truncating, the chlorophyll antenna size of the photosystems can improve photosynthetic solar energy conversion efficiency and productivity up to 3-fold. Generation of truncated light-harvesting chlorophyll antenna size (tla) strains, in all classes of photosynthetic organisms would help to alleviate excess absorption of sunlight and the ensuing wasteful dissipation of excitation energy, and to maximize solar-to-product energy conversion efficiency and photosynthetic productivity in high-density mass cultivations. The tla concept may find application in the commercial exploitation of microalgae and plants for the generation of biomass, biofuels, chemical feedstocks, as well as nutraceuticals and pharmaceuticals.     

Combinatorial de novo design and application of a biomimetic affinity ligand for the purification of human anti‐HIV mAb 4E10 from transgenic tobacco

Monoclonal anti‐HIV antibody 4E10 (mAb 4E10) is one of the most broadly neutralizing antibodies against HIV, directed against a specific epitope on envelope protein gp41. In the present study, a combinatorial de novo design approach was used for the development of a biomimetic ligand for the affinity purification of mAb 4E10 from tobacco transgenic extract in a single chromatographic step. The biomimetic ligand (4E10lig) was based on a L ‐Phe/β‐Ala bi‐substituted 1,3,5‐triazine (Trz) scaffold (β‐Ala‐Trz‐L ‐Phe, 4E10lig) which potentially mimics the more pronounced electrostatic and hydrophobic interactions of mAb 4E10‐binding sequence determined by screening of a random peptide library. This library was comprised of Escherichia coli cells harboring a plasmid (pFlitrx) engineered to express a fusion protein containing random dodecapeptides that were inserted into the active loop of thioredoxin, which itself was inserted into the dispensable region of the flagellin gene. Adsorption equilibrium studies with this biomimetic ligand and mAb 4E10 determined a dissociation constant (K_D) of 0.41 ± 0.05 µM. Molecular modeling studies of the biomimetic ligand revealed that it can potentially occupy the same binding site as the natural binding core peptide epitope. The biomimetic affinity adsorbent was exploited in the development of a facile mAb 4E10 purification protocol, affording mAb 4E10 of high purity (approximately 95%) with good overall yield (60–80%). Analysis of the antibody preparation by SDS‐PAGE, enzyme‐linked immunosorbent assays (ELISA), and western blot showed that the mAb 4E10 was fully active and free of degraded variants, polyphenols, and alkaloids. Copyright © 2009 John Wiley & Sons, Ltd.     

Cloning and characterization of the trout perforin

The pore-forming protein, perforin is one of the effectors of cell-mediated killing. A perforin cDNA clone was isolated from rainbow trout (Oncorhynchus mykiss) after screening of a spleen cDNA library. The full-length cDNA is 2070 bp in size, encoding for a polypeptide of 589 amino acids. The predicted amino acid sequence of the trout perforin is 64, 58 and 40% identical to those of Japanese flounder, zebrafish and human perforins, respectively. Although its membrane attack complex/perforin (MACPF) domain is conserved, trout perforin shows low homology to human and trout terminal complement components (C6, C7, C8 and C9), ranging from 19 to 26% identity. Expression analysis reveals that the trout perforin gene is expressed in the blood, brain, heart, kidney, intestine and spleen. Phylogenetic analysis of proteins which belong to the MACPF superfamily clusters the trout perforin in the same group with other known perforins.     

Lifestyle Intervention Favorably Affects Weight Loss and Maintenance Following Obesity Surgery

The present study was designed to evaluate the 3 year effects of a lifestyle intervention on weight loss and maintenance, dietary, and physical activity habits and eating behavior of patients following vertical banded gastroplasty (VBG). Thirty severely obese female volunteers were included in the study and they were randomly assigned to one of two intervention groups: usual care (UC) or lifestyle intervention (LS) group. Patients were followed for 3 years postoperatively. Outcome measures included weight loss, dietary habits, physical activity level (PAL), and eating behavior changes. Weight was significantly lower in the LS group after 12 months (84.4 ± 3.9 kg vs. 98.4 ± 4.4 kg, P < 0.05), 24 months (83.0 ± 3.3 vs. 101.9 ± 5.3 kg, P < 0.05), and 36 months following surgery (84.2 ± 3.3 vs. 102.5 ± 3.5 kg, P < 0.05). Repeated measures ANOVA revealed significant differences between the two groups overall and at specific time points for the PAL and TV viewing. With regard to eating behavior, the LS group scored significantly better in total Dutch Eating Behavior Questionnaire (DEBQ), Restraint Eating and External Eating scales at all postoperative time points. Similarly, significant differences were found between the two groups in dietary intake. These findings outline the importance of lifestyle intervention on weight loss and maintenance following bariatric surgery. The favorable effects of lifestyle intervention may be through adoption of healthier eating behaviors and increased physical activity.     

Stochastic Analysis of the Motion of DNA Nanomechanical Bipeds

In this paper, we formulate and analyze a Markov process modeling the motion of DNA nanomechanical walking devices. We consider a molecular biped restricted to a well-defined one-dimensional track and study its asymptotic behavior. Our analysis allows for the biped legs to be of different molecular composition, and thus to contribute differently to the dynamics. Our main result is a functional central limit theorem for the biped with an explicit formula for the effective diffusivity coefficient in terms of the parameters of the model. A law of large numbers, a recurrence/transience characterization and large deviations estimates are also obtained. Our approach is applicable to a variety of other biological motors such as myosin and motor proteins on polymer filaments.     

A new methodology for rapid detection of Lactobacillus delbrueckii subsp. bulgaricus based on multiplex PCR

In this study we present a novel multiplex PCR assay for rapid and efficient detection of Lactobacillus delbrueckii subsp. bulgaricus. The accuracy of our method was confirmed by the successful identification of L. delbrueckii subsp. bulgaricus in commercial yoghurts and food supplements and it may be readily applied to the food industry.     

Heterologous Expression of the Mevalonic Acid Pathway in Cyanobacteria Enhances Endogenous Carbon Partitioning to Isoprene

Heterologous expression of the isoprene synthase gene in the cyanobacterium Synechocystis PCC 6803 conferred upon these microorganisms the property of photosynthetic isoprene （C5H8） hYdrocarbons production. Continuous production of isoprene from CO2 and H2O was achieved in the light, occurring via the endogenous methylerythritolphosphate （MEP） pathway, in tandem with the growth of Synechocystis. This work addressed the issue of photosynthetic carbon partitioning between isoprene and biomass in Synechocystis. Evidence is presented to show heterologous genomic integration and cellular expression of the mevalonic acid （MVA） pathway genes in Synechocystis endowing a non-native pathway for carbon flux amplification to isopentenyl-diphosphate （IPP） and dimethylallyl-diphosphate （DMAPP） precursors of isoprene. Heterologous expression of the isoprene synthase in combination with the MVA pathway enzymes resulted in photosynthetic isoprene yield improvement by approximately 2.5-fold, compared with that measured in cyanobacteria transformed with the isoprene synthase gene only. These results suggest that the MVA pathway introduces a bypass in the flux of endogenous cellular substrate in Synechocystis to IPP and DMAPP, overcoming flux limitations of the native MEP pathway. The work employed a novel chromosomal integration and expression of synthetic gene operons in Synechocystis, comprising up to four genes under the control of a single promoter, and expressing three operons simultaneously. This is the first time an entire biosynthetic pathway with seven recombinant enzymes has been heterologously expressed in a photosynthetic microorganism. It constitutes contribution to the genetic engineering toolkit of photosynthetic microorganisms and a paradigm in the pursuit of photosynthetic approaches for the renewable generation of high-impact products.     

Group Colocation Behavior in Technological Social Networks

We analyze two large datasets from technological networks with location and social data: user location records from an online location-based social networking service, and anonymized telecommunications data from a European cellphone operator, in order to investigate the differences between individual and group behavior with respect to physical location. We discover agreements between the two datasets: firstly, that individuals are more likely to meet with one friend at a place they have not visited before, but tend to meet at familiar locations when with a larger group. We also find that groups of individuals are more likely to meet at places that their other friends have visited, and that the type of a place strongly affects the propensity for groups to meet there. These differences between group and solo mobility has potential technological applications, for example, in venue recommendation in location-based social networks.