The tetrapeptide Z‐Leu‐Aib‐Pro‐Val‐OBg monohydrate

The intramolecular hydrogen‐bonding pattern of Z‐Leu‐Aib‐Pro‐Val‐OBg monohydrate [(N‐benzhydryl­amino)­carbonyl­methyl N‐benzyl­oxy­carbonyl‐α‐amino­isobutyryl­prolyl­valinate monohydrate], C₄₃H₅₅N₅O₈·H₂O, is unusual for a tetrapeptide because, in addition to a 14 hydrogen bond, a second hydrogen bond of the type 15 is formed. This folding reflects the intramolecular hydrogen‐bonding pattern that this amino acid sequence adopts in the naturally occurring peptaibol alamethicin.     

Pentopyranosyl Oligonucleotide Systems. 9th Communication

Pyranosyl‐RNA (‘p‐RNA’ ) is an oligonucleotide system isomeric to natural RNA and composed of the very same building blocks as RNA. Its generational, chemical, and informational properties are deemed to be those of an alternative nucleic acid system that could have been a candidate in Nature's evolutionary choice of the molecular basis of genetic function. We consider the study of the chemistry of p‐RNA as etiologically relevant in the sense that knowledge of its structural, chemical, and informational properties on the chemical level offers both a perspective and reference points for the recognition of specific structural assets of the RNA structure that made it the (supposedly) superior system among possible alternatives and, therefore, the system that became part of biology as we know it today. The paper describes the chemical synthesis of β‐d‐ (and L )‐ribopyranosyl‐(4′→2′)‐oligonucleotide sequences, presents a resume of their structural and chemical properties, and cautiously discusses what we may and may not have learned from the pyranosyl isomer of RNA with respect to the conundrum of RNA's origin.     

Transgenic Expression and Functional Characterization of Human Platelet Derived Growth Factor BB (hPDGF-BB) in Tobacco (Nicotiana tabacum L.)

Recombinant human platelet derived growth factor BB (rhPDGF-BB) is clinically approved for treating diabetic neuropathic ulcers. Plant-based expression systems offer less expensive ways of producing recombinant drugs, which do not require purification for clinical use. From this perspective, rhPDGF-BB is an ideal candidate for expression in plants as it can be applied topically. Here, we report a proof of concept study, in which rhPDGF-BB was expressed in tobacco plants, and its biological activity was tested in vitro. The mature human platelet derived growth factor BB (hPDGF-BB) gene was codon-optimized for tobacco and fused with ER targeting and retention signals, 5′ and 3′ UTRs of arc5-1 gene along with CaMV 35S promoter, and then, transferred by Agrobacterium-mediated transformation. Gene and protein expression of hPDGF-BB were confirmed by PCR and immunoblot studies. Bioactivity of hPDGF-BB expressed protein was determined by in vitro assays such as proliferation and migration in NIH3T3 cells. Our data reveals that total soluble proteins containing hPDGF-BB from transgenic plants showed a 4.5-fold increase in fibroblast proliferation compared to non-transgenic plants. Furthermore, plant-made rhPDGF-BB induced chemotaxis of treated cells and promoted wound healing in vitro. These results clearly demonstrate that functionally active rhPDGF-BB protein can be produced in plants and might have therapeutic benefits.     

Genotoxicity and Cytotoxicity of 4-Nonylphenol Ethoxylate on Lymphocytes as Assessed by the Comet Assay

Surfactants, which are prevalent at industrial sites and in the environment generally, are potential risk factors in human carcinogenesis. The widespread industrial use of surfactants such as 4-alkylphenol ethoxylates and their prevalence in many cleaning products have provoked studies about surfactant concentrations in water and their toxicity levels. Up to now, these substances have mainly been tested on aquatic organisms. Though tests on human cell lines are rare. The alkaline Comet assay was performed to evaluate the genotoxicity of 4-nonylphenol ethoxylate, a biodegradable product of 4-alkylphenol ethoxylate, in human lymphocytes. Concentrations tested ranged from 0.15 to 150 µg/mL. Test concentrations of 10 to 15 µg/mL caused an increase level of DNA migration in human cells, but without inducing excessive toxicity (viability > 80%). Though induced levels of DNA migration starting at concentrations of 30 µg/mL may have been due to excessive levels of cytotoxicity (viability < 70%). Based on these data, 4-nonylphenol ethoxylate can induce DNA damage in human lymphocytes but at higher concentrations than are normally found in river or drinking water. However, considering the prevalence of surfactants, the measured genotoxicity of these substances is of concern. Further investigations on human target cells are necessary to evaluate the carcinogenic impact of surfactants and reconsider their environmental acceptance.     

First synthesis of a beta(2)-homoamino acid by enantioselective catalysis

The enantioselective conjugate addition of diethylzinc to the activated nitroolefin methyl 3-nitropropenoate is efficiently catalyzed by copper(I) complexes with BINOL-based enantiopure phosphoramidite ligands. The nitroolefin moiety acts as the predominant Michael acceptor, giving rise to the unambiguous formation of 2-alkyl-3-nitro-propanoates. Moderate to excellent enantioselectivities and high chemical yields are obtained. The product can easily be transformed into a beta(2)-homoamino acid. [reaction--see text]     

Making Use of the Direct Process Residue: Synthesis of Bifunctional Monosilanes

The industrial production of monosilanes Me_nSiCl_4−n (n=1–3) through the Müller–Rochow Direct Process generates disilanes Me_nSi₂Cl_6−n (n=2–6) as unwanted byproducts (“Direct Process Residue”, DPR) by the thousands of tons annually, large quantities of which are usually disposed of by incineration. Herein we report a surprisingly facile and highly effective protocol for conversion of the DPR: hydrogenation with complex metal hydrides followed by Si−Si bond cleavage with HCl/ether solutions gives (mostly bifunctional) monosilanes in excellent yields. Competing side reactions are efficiently suppressed by the appropriate choice of reaction conditions.     

Influence type of natural rubber on properties of green biodegradable thermoplastic natural rubber based on poly(butylene succinate)

Green biodegradable thermoplastic natural rubber (GB‐TPNR) based on simple blend of natural rubber (NR) and poly(butylene succinate) (PBS) was prepared using three NR alternatives: unmodified NR and epoxidized NR with 25‐ or 50‐mol% epoxide (ie, ENR‐25 or ENR‐50). It was found that ENR‐50/PBS blend showed the best compatibility, which resulted in superior mechanical and thermal properties with the highest crystallinity of the PBS phase, on comparing with the ENR‐25/PBS and NR/PBS blends. This might be attributed to stronger chemical interactions between the epoxide groups in ENR‐50 and the polar functional groups in PBS, which were confirmed by Fourier transform infrared (FTIR). Furthermore, scanning electron microscopy (SEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM) micrographs of ENR‐50/PBS blend revealed phase separation with finer‐grained cocontinuous structure than in ENR‐25/PBS and NR/PBS simple blends. Furthermore, the chemical interactions in ENR‐50/PBS blend enhanced the resistance to accelerated weathering.     

Applications of magnetic materials separation in biological nanomedicine

As a result of their advantages for superparamagnetic properties, good biocompatibility, and high binding capacity, functionalized magnetic materials became widely popular over the past couple of decades, being applied on large scale in various processes of sample preparation for biomedicine. In this work, we perform an in‐depth review on the current progress in the field of magnetic bead separation, discussing in detail the physical basis of this process, various synthesis methods and surface modification strategies. We place special focus of attention as well on the latest applications of magnetic polymer microspheres in cell separation, protein purification, immobilized enzyme, nucleic acid separation, and extraction of bioactive compounds with low molecular weight. Existing problems are highlighted and possible trends of magnetic separation techniques for biomedicine in the future are proposed.