Photochemical covalent binding of urocanic acid to polynucleic acids

Photolysis of E-[ring-2-14C]urocanic acid (UA) with native or denatured calf thymus DNA leads to covalent binding of the radiolabel to the nucleic acid. A similar observation is made upon photolysis of the labeled UA with the polyribonucleotides, in which case a strong preference is observed for binding to poly[U]. DNA or poly[U], which had been reacted with UA and purified by dialysis and multiple precipitations, releases UA upon further irradiation with 254 nm light (as expected for cyclobutane adducts). Quantum efficiencies for binding of the UA to native DNA have been measured at 308 and 266 nm and are 0.30 x 10(-5) and 1.3 x 10(-4), respectively, at comparable reactant concentrations. The large increase at the shorter wavelength (where DNA absorption is more competitive) is taken as evidence for the primary role of a DNA excited state in initiating the binding reaction(s).     

Ultra-compact Spatial Terahertz Switch Based on Graphene Plasmonic-Coupled Waveguide

We are proposing graphene (G)-based multilayered plasmonic spatial switch, operating at 10 THz. It is composed of hBN/Ag/hBN/G/hBN/G/hBN/SiO₂/p⁺-Si multilayers. When a 10-THz transverse magnetic (TM)-polarized signal is normally incident upon the structure top surface, the nanoaperture devised in the Ag nanolayer, acting as a grating, excites surface plasmons at the top graphene micro-ribbons/hBN interface. These surface plasmons depending on the graphenes chemical potentials can be coupled to the lower-right or left graphene micro-ribbons and continue to propagate laterally towards the corresponding output port. Numerical simulations show that a change of ∆V_G ≈ ± 2.7 V in the voltage, applied to the gated micro-ribbons, can modulate their chemical potentials sufficiently to switch the right (left) output port from ON (OFF) to OFF(ON) and vice versa. Besides its low power consumption, the switch ultra-small dimensions make it a potential spatial router suitable for THz-integrated circuit applications.

     

A novel regulatory role of TRAPPC9 in L-plastin-mediated osteoclast actin ring formation

Trafficking protein particle complex 9 (TRAPPC9) is a major subunit of the TRAPPII complex. TRAPPC9 has been reported to bind nuclear factor κB kinase subunit β (IKKβ) and NF-kB-inducing kinase (NIK) where it plays a role in the canonical and noncanonical of nuclear factor-κB (NF-kB) signaling pathways, receptively. The role of TRAPPC9 in protein trafficking and cytoskeleton organization in osteoclast (OC) has not been studied yet. In this study, we examined the mRNA expression of TRAPPC9 during OC differentiation. Next, we examined the colocalization of TRAPPC9 with cathepsin-K, known to mediate OC resorption suggesting that TRAPPC9 mediates the trafficking pathway within OC. To identify TRAPPC9 protein partners important for OC-mediated cytoskeleton re-organization, we conducted immunoprecipitation of TRAPPC9 in mature OCs followed by mass spectrometry analysis. Our data showed that TRAPPC9 binds various protein partners. One protein with high recovery rate is L-plastin (LPL). LPL localizes at the podosomes and reported to play a crucial role in actin aggregation thereby actin ring formation and OC function. Although the role of LPL in OC-mediated bone resorption has not fully reported in detail. Here, first, we confirmed the binding of LPL to TRAPPC9 and, then, we investigated the potential regulatory role of TRAPPC9 in LPL-mediated OC cytoskeleton reorganization. We assessed the localization of TRAPPC9 and LPL in OC and found that TRAPPC9 is colocalized with LPL at the periphery of OC. Next, we determined the effect of TRAPPC9 overexpression on LPL recruitment to the actin ring using a viral system. Interestingly, our data showed that TRAPPC9 overexpression promotes the recruitment of LPL to the actin ring when compared with control cultures. In addition, we observed that TRAPPC9 overexpression reorganizes actin clusters/aggregates and regulates vinculin recruitment into the OC periphery to initiate podosome formation.     

The congenital cataract-causing mutations P20R and A171T are associated with important changes in the amyloidogenic feature,structure and chaperone-like activity of human αB-crystallin

Cataract is the major reason for human blindness worldwide. α-Crystallin, as a key chaperone of eye lenses, keeps the lenticular tissues in its transparent state over time. In this study, cataract-causing familial mutations, P20R and A171T, were introduced in CRYАB gene. After successful expression in Escherichia coli and subsequent purification, the recombinant proteins were subjected to extensive structural and functional analyses using various spectroscopic techniques, gel electrophoresis, and electron microscopy. The results of fluorescence and Raman assessments suggest important but discreet conformational changes in human αB-Cry upon these cataractogenic mutations. Furthermore, the mutant proteins exhibited significant secondary structural alteration as revealed by FTIR and Raman spectroscopy. An increase in conformational stability was seen in the human αB-Cry bearing these congenital cataractogenic mutations. The oligomeric size distribution and chaperone-like activity of human αB-Cry were significantly altered by these mutations. The P20R mutant protein was observed to loose most of the chaperone-like activity. Finally, these cataractogenic mutant proteins exhibited an increased propensity to form the amyloid fibrils when incubated under environmental stress. Overall, the structural and functional changes in mutated human αB-Cry proteins can shed light on the pathogenic development of congenital cataracts.     

Variation of Essential Oil Content and Composition,Phenolics, and Yield Related Traits Using Different Pollination Systems in Populations of Thymus Species

The production of self-pollinated plants could be important for improving medicinal plants secondary metabolites. In this study, 11 Thymus populations from eight species were evaluated to determine the effect of self and open pollination on agro-morphological characteristics, total phenolic content (TPC), essential oil (EO) content, and EO components. Inbreeding led to some positive effects of above mentioned traits in most of the studied populations. Total phenolic content ranged from 7.07 to 52.69 mg tannic acid equivalents (TAE) g⁻¹ dry weight (DW) in open pollinated derived populations, while it varied from 1.2 to 55.03 mg TAE g⁻¹ DW in self-pollinated ones. Under open and self-pollination condition, the highest EO content was obtained in T. trautvetteri (3.37 %) and T. pubescens (1.96 %), respectively. Gas chromatography-mass spectrometry (GC/MS) identified 42 compounds including thymol, carvacrol, linalool, p-cymene, γ-terpinene, terpinen-4-ol, and α-terpineol as the main compounds. In most cases, selfed plants compared to open pollinated ones, revealed higher thymol content. T. daenensis-1 showed a significant increase in thymol content (from 25.22 % to 74.3 %) due to self-pollination. Moreover, self-pollination led to emergence of some new compounds. Carvacrol methyl ether was the constituents of Thymus EO that are being reported in self-pollinated populations. Finally, inbreeding in Thymus might be suggested as a useful tool to increase genetic homogeneity for the selection of superior plants for improving secondary metabolite.     

Binding of linker histones to the core nucleosome

Binding of chicken erythrocyte linker histones H1/H5 to the core nucleosome has been studied. Histones H1/H5 bind very efficiently to the isolated core nucleosome in vitro. The binding of linker histones to the core nucleosome is associated with aggregation of the particles. Approximately one molecule of linker histone binds per core nucleosome in the aggregates, irrespective of the concentration of the linker histones and the salt used. Histone H5 shows greater binding affinity to the core nucleosome as compared to H1. The carboxyl-terminal fragment of the linker histones binds strongly to the core nucleosome while the binding of the central globular domain is weak. Each core nucleosome is capable of binding two molecules of carboxyl-terminal fragment of linker histone. The core nucleosome containing one molecule of carboxyl-terminal fragment of linker histone requires higher salt concentration for aggregation while the core nucleosome containing two molecules of carboxyl-terminal fragment of linker histone can self-associate even at lower salt concentrations. On the basis of these results we are proposing a novel mechanism for the condensation of chromatin by linker histones and other related phenomena.     

Development of a single probe for documentation of chimerism following bone marrow transplantation.

Although numerous genetic markers are available for studying chimerism after bone marrow transplantation (BMT), there remains a need for a practical and highly informative method that is applicable in the early posttransplantation period. Using DNA restriction-fragment-length polymorphisms (RFLPs), we have evaluated the feasibility of developing a single synthetic oligonucleotide probe to study post-BMT chimerism. We have thus tested three candidate probes, termed O-3315-32, O-3315-80, and O-AY-29, that are homologous to tandemly repetitive sequences. Our results demonstrated donor-specific and recipient-specific fragments in 11 of 11 HLA-matched sibling pairs tested using probes O-3315-32 and O-3315-80. When probe O-AY-29 was used, 14 of 17 sibling pairs showed both donor and recipient markers, one had only a recipient marker, and two were identical. We showed that each of the three synthetic probes was effective in documenting donor marrow engraftment, mixed hematopoietic chimerism, the patient's pre-BMT phenotype (by using cultured skin fibroblasts obtained after BMT), and the origin of the malignant hematopoietic cells (i.e., of donor or recipient origin) in patients who developed recurrent hematologic malignancy following BMT. Compared with the use of cloned genomic probes, there are several important advantages to the use of synthetic oligonucleotide probes in studying post-BMT chimerism. Synthetic probes have absolute hybridization specificity and can be designed to suit the purposes of an individual study, since they have adjustable specificity that can be altered by changes in the length of the probe and by changes in the hybridization temperature. A single synthetic probe analogous to several highly polymorphic loci can have a polymorphism information content sufficiently high so that all but a small percentage of BMT patients could be followed easily; for example, if a probe were complementary to three highly polymorphic unlinked loci, it would discriminate approximately 98% of sibling donor/recipient pairs. This would be accomplished using only one restriction-endonuclease digestion and only one gel electrophoresis. Since other genetic markers, e.g., red blood cell antigens, immunoglobulin allotypes, and chromosome analysis, are not uniformly informative and, in some cases, cannot be used in the early posttransplantation period, the use of synthetic oligonucleotide probes for analysis of DNA RFLP is emerging as the method of choice for studies of post-BMT chimerism. This method will allow for the development of new knowledge that has not been possible with previous methods.