Theoretical study of two-photon absorption properties and up-conversion efficiency of new symmetric organic π-conjugated molecules for photovoltaic devices

Organic material with high intensity of two-photon absorption (TPA) induced fluorescence can be used as the frequency up-converter materials for improving efficiency of the solar cells. In this work, the organic molecular structures were designed by symmetrically grafting two elongated conjugated linkers on a conjugated core and then adding donor groups at both terminals. Fluorene derivatives as a core acceptor, phenylethynyl as the conjugated linker and diphenylamino or methyl-9H-carbozole as the donor end groups were selected. Quantum mechanical modeling techniques were applied to investigate the molecular electronic structure and properties. Absorption properties of these novel π-conjugated organic molecules were studied. The TPA cross-sections of these derivatives were calculated using few-states models, respectively. The effects of donor and acceptor groups on the TPA behaviors of these designed molecules were investigated. The up-conversion efficiency of designed molecules was also calculated.     

‘Anticalins’: a new class of engineered ligand-binding proteins with antibody-like properties

The development of soluble receptor proteins that recognise given target molecules — ranging from small chemical compounds to macromolecular structures at a cell surface, for example — is of ever increasing importance in the life sciences and biotechnology. For the past century this area of application was dominated by antibodies, which were traditionally generated via immunisation of animals but have recently also become available by means of protein engineering methods. The so-called ‘anticalins’ offer an alternative type of ligand-binding proteins, which has been constructed on the basis of lipocalins as a scaffold. The central element of this protein architecture is a β-barrel structure of eight antiparallel strands, which supports four loops at its open end. These loops form the natural binding site of the lipocalins and can be reshaped in vitro by extensive amino acid replacement, thus creating novel binding specificities. The bilin-binding protein (BBP) was employed as a model system for the preparation of a random library with 16 selectively mutagenized residues. Using bacterial phagemid display and colony screening techniques, several lipocalin variants — termed anticalins — have been selected from this library, exhibiting binding activity for compounds like fluorescein or digoxigenin. Anticalins possess high affinity and specificity for their prescribed ligands as well as fast binding kinetics, so that their functional properties are similar to those of antibodies. Compared with them, they exhibit however several advantages, including a smaller size, composition of a single polypeptide chain, and a simple set of four hypervariable loops that can be easily manipulated at the genetic level. Apart from haptenic compounds as targets, anticalins should also be able to recognise macromolecular antigens, provided that the random library is accordingly designed. Hence, they should not only serve as valuable reagents for bioanalytical purposes, but may also have a potential in replacing antibodies for medical therapy.     

Theoretical investigation of the two-photon absorption properties of 3,6-bis(4-vinylpyridinium) carbazole derivatives—new biological fluorescent probes

The present study focuses on a series of carbazole derivatives, which are being investigated as potential two-photon fluorescent probes (TFP) for DNA detection and two-photon bioimaging. The geometric structures, electronic structures, and the one-photon (OPA) and two-photon (TPA) absorption properties of 3,6-bis(1-methyl-4-vinylpyridinium) carbazole (BMVC) derivatives, as well as their dications and diiodized derivatives, were studied using density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) method. The results showed that the TPA spectra of the diiodized BMVC derivatives and their dications are all found in the near-infrared region (NIR). At the same time, the diiodized BMVC derivatives presented larger TPA cross-sections than the neutral BMVC derivatives and the dications. These theoretically derived values were also in good agreement with their corresponding experimentally observed values, and they indicated that the diiodized BMVC may be the form of this TFP that combines with DNA. The diiodized BMVC derivatives and the dications have the potential to be excellent TPA materials, especially when used as TFPs in nucleic acid imaging applications.     

Light absorption by isolated chloroplasts and leaves: effects of scattering and ‘packing’

Light absorption was quantified in the following systems: isolated chloroplasts and leaves of spinach (Spinacea oleracea L.), a mutant of geranium (Pelargonium zonale L.) widely differing in pigment content, and coleus (Coleus blumei Benth.) at different stages of leaf ontogenesis. For these species and pea (Pisum sativum L.), scattering-compensated absorption spectra of chloroplast suspensions are presented. Comparison of leaf and chloroplast spectra showed considerable changes in the extent of the ‘package’ effect and the lengthening of the effective optical path in a leaf. The difference between leaf and isolated chloroplast absorption could be quantitatively described by adapting Duysens’s treatment of flattening. It was found that the accumulation of chlorophyll in leaves is accompanied by a monotonous enhancement of the package effect. The results are discussed with special reference to the role of light scattering in leaf optics, light utilization in photosynthesis and wavelength-dependent light gradients in a leaf.     

Physiological and genomic characterization of a new ‘Candidatus Nitrotoga’ isolate

Oxidation of nitrite to nitrate is an important process in the global nitrogen cycle. Recent molecular biology-based studies have revealed that the widespread nitrite-oxidizing bacteria (NOB) belonging to the genus ‘Candidatus Nitrotoga’ may be highly important for the environment. However, the insufficient availability of pure Nitrotoga cultures has limited our understanding of their physiological and genomic characteristics. Here, we isolated the ‘Ca. Nitrotoga’ sp. strain AM1P, from a previously enriched Nitrotoga culture, using an improved isolation strategy. Although ‘Ca. Nitrotoga’ have been recognized as cold-adapted NOB, the strain AM1P had a slightly higher optimum growth temperature at 23°C. Strain AM1P showed a pH optimum of 8.3 and was not inhibited even at high nitrite concentrations (20 mM). We obtained the complete genome of the strain and compared the genome profile to five previously sequenced ‘Ca. Nitrotoga’ strains. Comparative genomics suggested that lactate dehydrogenase may be only encoded in the strain AM1P and closely related genomes. While the growth yield of AM1P did not change, we observed faster growth in the presence of lactate in comparison to purely chemolithoautotrophic growth. The characterization of the new strain AM1P sheds light on the physiological adaptation of this environmentally important, but understudied genus ‘Ca. Nitrotoga’.     

A new synthetic method for ruthenium complexes of β-diketones from ‘ruthenium blue solution’ and their properties

The ‘ruthenium blue solution’ obtained by reducing hydrated ruthenium(III) trichloride with ethanol was used a convenient starting material in the synthesis of thirteen tris(β-diketonato)ruthenium (III) and six tris(β-diketonato)ruthenate(II) complexes. The procedure of preparing the ‘ruthenium blue solution’ requires no catalyst and is much simpler than the previous methods. A variety of complexes were synthesized in good yields with small changes of the conditions. The Hammett constants of the substituents on the ligand serve as a helpful guide for choosing the operating conditions for the preparation of β-substituted complexes. The yields of the complexes with β-substituted ligands are relatively small, since the presence of a bulky substituent at the β-position decreases the fraction of the enol form of the free ligand. The melting points, magnetic moments, R_f values in TLC, UV-Vis, IR, and ¹H NMR spectra were measured. The substituent effects on these properties are discussed.     

Characterization of ‘Sun II’ oat monosomics through C-banding and identification of eight new ‘Sun II’ monosomics

 Monosomics are a powerful tool for genetic mapping in allopolyploid plant species such as oat (Avena sativa L., 2n=6x=42). A C-banded karyotype of the oat cultivar Sun II was compared with previously described oat karyotypes and was used to identify the missing chromosome in each line of Sun II aneuploids. These included new aneuploids, isolated among derivatives of oat haploids obtained from Sun II oat×maize crosses, along with the original Sun II aneuploid set which had been obtained by cytological screening of a Sun II population for spontaneous aneuploids. Eight new Sun II monosomics were identified among the derivatives of haploids from the oat×maize crosses, to give a total of 18 unique Sun II monosomic/nullisomic lines. All seven C-genome chromosomes are represented by Sun II monosomics. Chromosomes 13, 14 and 17 are not represented by Sun II aneuploids but are found in the Kanota monosomic series. Therefore, monosomics of some form are now available for all 21 oat chromosomes. A reciprocal translocation involving chromosomes 3C and 14, found in a portion of the original set of Sun II monosomic lines, was also described. No new translocations were detected in the Sun II×maize crosses. Received: 11 December 1996 / Accepted: 15 July 1997     

Simulation of ‘stationary’ SAP and SEP phenomena by 2-dimensional potential field modelling

In order to model the distribution of potentials in the hand due to antidromic SAP propagation and in the body due to afferent conduction of the median nerve volley, 2-dimensional matrices of the appropriate shape were constructed, each containing a ‘generator’ consisting of up to 3 ‘source’ and 3 ‘sink’ points. The value of the field potential at other sites was calculated using a finite difference method.It was shown that the potential gradient is virtually zero in matrix zones which are separated from the region containing the generator by a constriction in the boundary of the conductor. Points on the far side of the constriction remain virtually equipotential, at a level determined by the potential at the junction. This is naturally influened by the proximity of the generator, so that as the generator approaches the constriction a potential difference will develop between points on the far side, irrespective of their distance from the junction, and other remote parts of the matrix. In the context of human SAPs and SEPs, such factors may be of paramount importance in the generation of so-called ‘stationary’ or ‘far-field’ potentials.With additional postulates concerning the manner in which the SAP is attenuated by the termination of axons as it propagates through the hand, and the course taken by the median nerve volley between the arm and the neck, it was possible to model the majority of stationary SAP phenomena described by Kimura et al. (1984), and also the distribution and latency of the P9 SEP component following median nerve stimulation.     

Triazole-curcuminoids: A new class of derivatives for ‘tuning’ curcumin bioactivities?

Curcumin is a unique blend of pharmacophores responsible for the pleiotropy of this natural pigment. In the present study we have replaced the 1,3-dicarbonyl moiety with a 1,2,3-triazole ring to furnish a new class of triazole-curcuminoids as a possible strategy to generate new compounds with different potency and selectivity compared to curcumin. We obtained a proof-of-principle library of 28 compounds tested for their cytotoxicity (SY-SY5Y and HeLa cells) and for their ability to inhibit NF-κB. Furthermore, we also generated 1,3-dicarbonyl curcuminoids of selected click compounds. Triazole-curcuminoids lost their ability to be Michael’s acceptors, yet maintained some of the features of the parent compounds and disclosed new ones. In particular, we found that some compounds were able to inhibit NF-κB without showing cytotoxicity, while others, unlike curcumin, activated NF-κB signalling. This validates the hypothesis that click libraries can be used to investigate the biological activities of curcumin as well as generate analogs with selected features.     

A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs

Stegosaurian dinosaurs have a quadrupedal stance, short forelimbs, short necks, and are generally considered to be low browsers. A new stegosaur, Miragaia longicollum gen. et sp. nov., from the Late Jurassic of Portugal, has a neck comprising at least 17 cervical vertebrae. This is eight additional cervical vertebrae when compared with the ancestral condition seen in basal ornithischians such as Scutellosaurus. Miragaia has a higher cervical count than most of the iconically long-necked sauropod dinosaurs. Long neck length has been achieved by ‘cervicalization’ of anterior dorsal vertebrae and probable lengthening of centra. All these anatomical features are evolutionarily convergent with those exhibited in the necks of sauropod dinosaurs. Miragaia longicollum is based upon a partial articulated skeleton, and includes the only known cranial remains from any European stegosaur. A well-resolved phylogeny supports a new clade that unites Miragaia and Dacentrurus as the sister group to Stegosaurus; this new topology challenges the common view of Dacentrurus as a basal stegosaur.     

‘Lollipop’-shaped helical structure of a hybrid antimicrobial peptide of temporin B-lipopolysaccharide binding motif and mapping cationic residues in antibacterial activity

BackgroundTemporins are attractive templates for the development of antibiotics. However, many temporins are inactive against Gram-negative bacteria. Previously, we demonstrated conjugation of a lipopolysaccharide binding motif peptide to temporins yielded hybrid non-haemolytic AMPs that killed several Gram-negative bacteria.MethodsWe carried out a systematic Ala replacement of individual cationic and polar amino acid residues of LG21, a hybrid AMP consisted of temporin B (TB) and LPS binding motif. These Ala containing analogs of LG21 were examined for antibacterial activity, cell membrane permeabilization and liposome leakage assays using optical spectroscopic methods. Atomic resolution structure of LG21 was determined in zwitterionic dodecyl phosphocholine (DPC) micelles by NMR spectroscopy.ResultsCationic residues in the LPS binding motif of LG21 were critical for bactericidal and membrane permeabilization. Detergent bound structure of LG21 revealed helical conformation containing extensive sidechain/sidechain packing including cation/π interactions in the LPS binding motif. The helical structure of LG21 resembled a ‘lollipop’ like shape that was sustained by a compacted bulky aromatic/cationic head with a comparatively thinner ‘stick’ at the N-terminal region. The ‘head’ of the structure could be localized into micelle-water interfacial region whereas the ‘stick’ region may be inserted into the hydrophobic core of micelle.ConclusionsThe LPS binding motif of LG21 played dominant roles in broad spectrum activity and the 3-D structure provided plausible mechanistic insights for permeabilization of bacterial membrane.General significanceHybrid AMPs containing LPS binding motif could be useful for the structure based development of broad spectrum antibiotics.     

Synthesis and biological evaluation of arylidene analogues of Meldrum’s acid as a new class of antimalarial and antioxidant agents

A series of arylidene analogues of Meldrum’s acid were synthesized and evaluated for in vitro antimalarial and antioxidant activities for the first time. The influence of various physico-chemical parameters such as dielectric constant (ε), donor number (DN), acceptor number (AN), hydrogen bond donor (HBD), hydrogen bond acceptor (HBA), and solubilizing power of the solvents on Meldrum’s acid anion generation and thus on promoting the Knoevenagel condensation of Meldrum’s acid with aryl aldehydes has been discussed. Five compounds 9l, 9m, 9n, 9r, and 9s were found to be most active against Plasmodium falciparum with IC₅₀ values in the range of 9.68–16.11 μM. Compound 9l exhibited the most potent antimalarial activity (IC₅₀ 9.68 μM). The compounds were also found to possess antioxidant activity when tested against DPPH and ABTS free radicals.     

Arabidopsis thaliana ‘extra-large GTP-binding protein’ (AtXLG1): a new class of G-protein

Heterotrimeric GTP-binding proteins, composed of , , and subunits, are involved in signal transduction pathways in animal and plant systems. In plants, physiological analyses implicate heterotrimeric G-proteins in ion channel regulation, light signaling, and hormone and pathogen responses. However, only one class of plant G genes has been identified to date. We have cloned a novel gene, Arabidopsis thaliana extra-large GTP-binding protein (AtXLG1). AtXLG1 appears to be a member of a small gene family and is transcribed in all tissues assayed: roots, leaves, stems, flowers, and fruits. The conceptually translated protein from AtXLG1 is 99 kDa, twice as large as typical G proteins. The carboxy-terminal half of the AtXLG1 protein has significant homology to animal and plant G proteins. This region includes a GTP-binding domain, a predicted helical domain, and an aspartate/glutamate-rich loop, which are characteristics of G's. Despite the absence of some of the amino acids implicated in GTP binding and hydrolysis by crystallographic and mutational analyses of mammalian G's, recombinant AtXLGl binds GTP with specificity. The amino-terminal region of AtXLGl contains domains homologous to the bacterial TonB-box, which is involved in energy transduction between the inner and outer bacterial membranes, and to zinc-finger proteins. Given the unique structure of AtXLG1, it will be of interest to uncover its physiological functions.     

A new North American therizinosaurid and the role of herbivory in ‘predatory’ dinosaur evolution

Historically, ecomorphological inferences regarding theropod (i.e. ‘predatory’) dinosaurs were guided by an assumption that they were singularly hypercarnivorous. A recent plethora of maniraptoran discoveries has produced evidence challenging this notion. Here, we report on a new species of maniraptoran theropod, Nothronychus graffami sp. nov. Relative completeness of this specimen permits a phylogenetic reassessment of Therizinosauria—the theropod clade exhibiting the most substantial anatomical evidence of herbivory. In the most comprehensive phylogenetic study of the clade conducted to date, we recover Therizinosauria as the basalmost maniraptoran lineage. Using concentrated changes tests, we present evidence for correlated character evolution among herbivorous and hypercarnivorous taxa and propose ecomorphological indicators for future interpretations of diet among maniraptoran clades. Maximum parsimony optimizations of character evolution within our study indicate an ancestral origin for dietary plasticity and facultative herbivory (omnivory) within the clade. These findings suggest that hypercarnivory in paravian dinosaurs is a secondarily derived dietary specialization and provide a potential mechanism for the invasion of novel morpho- and ecospace early in coelurosaurian evolution—the loss of obligate carnivory and origin of dietary opportunism.     

Evaluating the efficacy of biological and conventional insecticides with the new ‘MCD bottle’ bioassay

Background

Urban malaria is considered to be one of the most significant infectious diseases due to varied socioeconomic problems especially in tropical countries like India. Among the south Indian cities, Chennai is endemic for malaria. The present study aimed to identify the hot spots of malaria prevalence and the relationship with other factors in Chennai during 2005-2011.

Methods

Data on zone-wise and ward-wise monthly malaria positive cases were collected from the Vector Control Office, Chennai Corporation, for the year 2005 to 2011 and verified using field data. This data was used to calculate the prevalence among thousand people. Hotspot analysis for all the years in the study period was done to observe the spatial trend. Association of environmental factors like altitude, population density and climatic variables was assessed using ArcGIS 9.3 version and SPSS 11.5. Pearson’s correlation of climate parameters at 95% and 99% was considered to be the most significant. Social parameters of the highly malaria prone region were evaluated through a structured random questionnaire field survey.

Results

Among the ten zones of Chennai Corporation, Basin Bridge zone showed high malaria prevalence during the study period. The ‘hotspot’ analysis of malaria prevalence showed the emergence of newer hotspots in the Adyar zone. These hotspots of high prevalence are places of moderately populated and moderately elevated areas. The prevalence of malaria in Chennai could be due to rainfall and temperature, as there is a significant correlation with monthly rainfall and one month lag of monthly mean temperature. Further it has been observed that the socioeconomic status of people in the malaria hotspot regions and unhygienic living conditions were likely to aggravate the malaria problem.

Conclusion

Malaria hotspots will be the best method to use for targeting malaria control activities. Proper awareness and periodical monitoring of malaria is one of the quintessential steps to control this infectious disease. It has been argued that identifying the key environmental conditions favourable for the occurrence and spread of malaria must be integrated and documented to aid future predictions of malaria in Chennai.