Regenerated silk fibroin solutions (RSF) are produced by dissolving degummed silk fibers in water. We have observed that RSF solutions at a concentration less than 15 % by weight exhibit an unusual gel-like response in conventional shear rheology measurements. At higher concentrations, the response is predominantly viscous (or liquid-like). We have probed this counterintuitive behavior of silk fibroin solutions by using microrheology, and interfacial rheometry. Scattering techniques were also used to understand the microstructure of RSF solutions as a function of the concentration. Our studies suggest that the gel-like response of the RSF solution may result from the formation of an interfacial film at the air–solution interface, which dominates the bulk rheological response. 相似文献
Siderophoregenic Bacillus strain DET9 has been selectively isolated from dairy waste. It was evaluated for probiotic characteristics and susceptibility
pattern against antibiotics. Its spores showed excellent tolerance to simulated gastrointestinal tract conditions and exhibited
antimicrobial activity against organisms such as Escherichia coli, Micrococcus flavus, and Staphylococcus aureus. Its susceptibility to antibiotics reduces the prospect to donate resistance determinants if administered in the form of probiotic
preparations. It was observed to produce ∼60 mg/l catecholate type of siderophore under iron stressed conditions, identified
as a 2,3-dihydroxy benzoic acid by high-performance liquid chromatography, infrared spectroscopy, nuclear magnetic resonance,
and mass spectral analysis. Partial 16S-rRNA gene sequencing analysis shows that the isolate exhibited homology with Bacillus thuringiensis and Bacillus weihenstephanensis, whereas biochemical characterization revealed its novelty. DET9 exhibited no mortality of fishes in a 60-day trial, when
fishes (surfi tetra) were challenged up to 100 ppm cell concentration, with their daily diet. 相似文献
In this work, we describe a simple spin-coating deposition technique for lead sulphide (PbS) and cadmium sulphide (CdS) films from a methanolic metal–thiourea complex. The characterization of the films by X-ray diffraction and X-ray photoelectron spectroscopy techniques revealed that pure cubic phase PbS and CdS layers were formed via this method. As shown by atomic force microscopy and scanning electron microscopy results, both films were homogeneous and presented a smooth surface. Optical properties showed that the energy band gap of PbS and CdS films were around 1.65 and 2.5 eV, respectively. The PbS film is p-type in nature with an electrical conductivity of around 0.8 S/cm. The hole concentration and mobility were 2.35 × 1018 cm?3 and 2.16 × 10?3 cm2/V/s, respectively, as determined from Hall measurement. Both films were used to develop a thin film solar cell device of graphite/PbS/CdS/ITO/glass. Device characterization showed the power conversion efficiency of around 0.24 %. The corresponding open circuit voltage, short circuit current and fill factor were 0.570 V, 1.32 mA/cm2 and 0.32, respectively. 相似文献
Reactions catalyzed by artificial allosteric enzymes, chimeric proteins with fused biorecognition and catalytic units, were used to mimic multi-input Boolean logic systems. The catalytic parts of the systems were represented by pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH). Two biorecognition units, calmodulin or artificial peptide-clamp, were integrated into PQQ-GDH and locked it in the OFF or ON state respectively. The ligand-peptide binding cooperatively with Ca2+ cations to a calmodulin bioreceptor resulted in the enzyme activation, while another ligand-peptide bound to a clamp-receptor inhibited the enzyme. The enzyme activation and inhibition originated from peptide-induced allosteric transitions in the receptor units that propagated to the catalytic domain. While most of enzymes used to mimic Boolean logic gates operate with two inputs (substrate and co-substrate), the used chimeric enzymes were controlled by four inputs (glucose – substrate, dichlorophenolindophenol – electron acceptor/co-substrate, Ca2+ cations and a peptide – activating/inhibiting signals). The biocatalytic reactions controlled by four input signals were considered as logic networks composed of several concatenated logic gates. The developed approach allows potentially programming complex logic networks operating with various biomolecular inputs representing potential utility for different biomedical applications. 相似文献
In continuation of our efforts to discover novel nitric oxide-releasing non-steroidal anti-inflammatory drugs (NO-NSAIDs) as potentially "Safe NSAIDs," we report herein the design, synthesis and evaluation of 21 new NO-NSAIDs of commonly used NSAIDs such as aspirin, diclofenac, naproxen, flurbiprofen, ketoprofen, sulindac, ibuprofen and indomethacin. These prodrugs have NO-releasing disulfide linker attached to a parent NSAID via linkages such as an ester (compounds 9-16), a double ester (compounds 17-24), an imide (compounds 25-30) or an amide (compounds 31-33). Among these NO-NSAIDs, the ester-containing NO-aspirin (9), NO-diclofenac (10), NO-naproxen (11), and the imide-containing NO-aspirin (25), NO-flurbiprofen (27) and NO-ketoprofen (28) have shown promising oral absorption, anti-inflammatory activity and NO-releasing property, and also protected rats from NSAID-induced gastric damage. NO-aspirin compound 25, on further co-evaluation with aspirin at equimolar doses, exhibited comparable dose-dependent pharmacokinetics, inhibition of gastric mucosal prostaglandin E(2) (PGE(2)) synthesis and analgesic properties to those of aspirin, but retained its gastric-sparing properties even after doubling its oral dose. These promising NO-NSAIDs could therefore represent a new class of potentially "Safe NSAIDs" for the treatment of arthritic pain and inflammation. 相似文献
The structure of lysozyme-sodium dodecyl sulfate (SDS) complexes in solution is studied using small-angle X-ray scattering (SAXS). The SAXS data cannot be explained by the necklace and bead model for unfolded polypeptide chain interspersed with surfactant micelles. For the protein and surfactant concentrations used in the study, there is only marginal growth of SDS micelles as they complex with the protein. Being a small and rather rigid protein, lysozyme can penetrate the micellar core which is occupied by flexible and disordered paraffin chains and also the shell occupied by the hydrated head groups. A partially embedded swollen micellar model seems appropriate and describes well the scattering data. The SAXS intensity profiles are analyzed by considering the change in the electron scattering length density of the micellar core and shell due to complexation with protein and treating the intermicellar interaction using rescaled mean spherical approximation (RMSA) for charged spheres. 相似文献
Neuroinflammation is one of the detrimental factors leading to neurodegeneration in Alzheimer’s disease (AD) and other neurodegenerative disorders. The activation of microglial neurokinin 1 receptor (NK1R) by substance P (SP) enhances neuroinflammation which is mediated through pro-inflammatory pathways involving NFkB, ERK1/2, and P38 and thus projects the scope and importance of NK1R inhibitors. Emphasizing the inhibitory role of N Acetyl l Tryptophan (l-NAT) on NK1R, this is the first in silico screening of l-NAT mediated NK1R antagonism. In addition, FDA- approved ligands were screened for their potential NK1R antagonism. The l-NAT was docked in XP (Extra Precision) mode while FDA-approved ligands were screened in HTVS (High Throughput Virtual Screening), SP (Standard Precision), and XP mode onto NK1R (PDB:6HLO). The l-NAT and top 3 compounds FDA-approved ligands were subjected to molecular dynamics (MD) studies of 100 ns simulation time. The XP docking of l-NAT, indacaterol, modafinil and alosetron showed good docking scores. Their 100 ns MD showed brief protein–ligand interactions with an acceptable root mean square deviation. The protein–ligand contacts depicted pi-pi stacking, pi-cation, hydrogen bonds, and water bridges with the amino acids necessary for NK1R inhibition. The variable colour band intensities on the protein–ligand contact map indicated their binding strength with amino acids. The molecular mechanics/generalized born surface area (MM-GBSA) scores suggested favourable binding free energy of the complexes. Thus, our study predicted the ability of l-NAT, indacaterol, modafinil, and alosetron as capable NK1R inhibitors that can aid to curb neuroinflammation in conditions of AD which could be further ascertained in subsequent studies.
The uniform aqueous dispersion of carbon nanotubes (CNTs) is a vital but challenging task required for their utilization in most technologies. We propose and demonstrate a technique based on forward- and side-scatter analysis on a flow cytometer to characterize the components in a dispersion of multiwalled CNTs (MWCNTs). The method simultaneously distinguishes various MWCNT components such as short and long CNTs, nanotube bundles, and particulates. It also detects the emergence of new CNT populations as a result of centrifugation. We use this method, together with classical methods such as UV and Raman spectroscopy, to observe and study the multistep MWCNT dispersion process in various surfactants (Pluronic, Triton X-100, sodium dodecyl sulfate, and cetyl trimethylammonium bromide). On the basis of the distinct scatter patterns obtained, we confirm and elaborate the surfactant-assisted unzipping mechanism of MWCNT dispersion. We also show that the ultrasonic energy spent after MWCNT unbundling and unwinding can be minimized and the process optimized for each surfactant by correct end point detection through scatter analysis. The ability to enrich nanotube population in dispersion by using the sorting mode of a flow cytometer is confirmed by electron microscopy and Raman spectroscopy. This method can thus be used for observing and enriching MWCNT components and as a complementary technique to UV spectroscopy for studying and optimizing MWCNT dispersion in surfactants. 相似文献