Kinetics of cooperative conformational transitions of lineal biopolymers

Cooperative conformational transitions of proteins and nucleic acids are of decisive importance to many processes of molecular biology, and particularly to their regulation. They proceed via numerous interdependent elementary processes, and their kinetics are therefore often complicated. They are frequently also very fast. However, kinetic analyses can be carried out by chemical relaxation methods. The theoretical interpretation is comparatively simple in the case of linear biopolymers. When the linear Ising model extended for kinetics was applied to model peptides and polynucleotides, it provided an insight into the fundamental principles of cooperative transformations.     

Ion mobility–mass spectrometry: a new paradigm for proteomics

Matrix-assisted laser desorption/ionization (MALDI) coupled with ion mobility–mass spectrometry (IM–MS) provides a rapid (μs–ms) means for the two-dimensional (2D) separation of complex biological samples (e.g., peptides, oligonucleotides, glycoconjugates, lipids, etc.), elucidation of solvent-free secondary structural elements (e.g., helices, β-hairpins, random coils, etc.), rapid identification of post-translational modifications (e.g., phosphorylation, glycosylation, etc.) or ligation of small molecules, and simultaneous and comprehensive sequencing information of biopolymers. In IM–MS, protein-identification information is complemented by structural characterization data, which is difficult to obtain using conventional proteomic techniques. New avenues for enhancing the figures of merit (e.g., sensitivity, limits of detection, dynamic range, and analyte selectivity) and optimizing IM–MS experimental parameters are described in the context of deriving new information at the forefront of proteomics research.     

Temperature-sensitive polypeptide brushes-coated mesoporous silica nanoparticles for dual-responsive drug release

A multifunctional nanohybrid based on mesoporous silica nanoparticle and biocompatible polypeptide was fabricated for targeted and dual-responsive therapy of tumor cells.     

Solid-state,optical-rotation measurements on macromolecules using powder-suspensions

Summary We report techniques for measuring optical rotation of suspended solids, including dissymmetric molecular crystals (e.g. sodium chlorate and bromate), synthetic polymers, polypeptides and biopolymers. Examples include poly(triphenylmethyl methacrylate), poly-S-lactide, poly-L-hydroxyproline, hemocyanine, cellulose acetate andRNA. The results indicate that optical rotation measurements are sensitive to differences in secondary structure and can serve as a probe for structural differences between solid-state and solution.

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Messung der optischen Rotation von Makromolekülen im Festzustand unter Verwendung von Pulversuspensionen

Zusammenfassung Es wird über eine Methode zur Messung der optischen Rotation von Festkörpern in Suspensionen berichtet, wobei dissymetrische Kristalle (z. B. Natriumchlorat und -bromat), synthetische Polymere, Polypeptide und Biopolymere behandelt werden. Die Beispiele umfassen Poly(triphenylmethylmethacrylat), Poly-S-lactid, Poly-L-hydroxyprolin, Hemocyanin, Celluloseacetat undRNA. Die Ergebnisse zeigen, daß die optischen Rotationen bezüglich Unterschiede in der Sekundärstruktur empfindlich sind und daß diese Messungen als ein Maß für Strukturunterschiede zwischen Festzustand und Lösung herangezogen werden können.

     

Ion-ion reactions for charge reduction of biopolymer at atmospheric pressure ambient

Extractive electrospray ionization source(EESI)was adapted for ion-ion reaction,which was demonstrated by using a linear quadrupole ion trap mass spectrometer for the first ion-ion reaction of biopolymers in the atmospheric pressure ambient.     

Chitosan-coated silver nanoparticles promoted antibacterial,antibiofilm, wound-healing of murine macrophages and antiproliferation of human breast cancer MCF 7 cells

In the present study, environmentally benign silver nanoparticles were synthesized using commercially purchased shrimp-shell chitosan as a capping agent. The synthesized chitosan-silver nanoparticles (Ch-AgNPs) were physico-chemically characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM) along with energy dispersive X-ray analysis (EDX), DLS and Zeta potential analysis. Ch-Ag NPs were crystalline, uniformly dispersed, and spherically shaped, with particle size between 8 and 48 nm. The average size of Ch-AgNPs was 21 nm. In-vitro anti-biofilm activity of Ch-AgNPs was tested against wound infection-causing pathogenic bacteria such as Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative). Ch-AgNPs displayed anti-biofilm activity in a dose-dependent manner. Light and confocal-laser scanning microscopy confirmed the significant inhibition of biofilm growth of S. aureus (85%) and P. aeruginosa (95%) at 100 μg mL⁻¹ of Ch-AgNPs. Moreover, Ch-AgNPs promoted wound healing by increasing the migration of RAW 264.7 murine macrophages cells at 75 and 100 μg mL⁻¹after 24 h. In addition, in vitro cytotoxicity of Ch-AgNPs against MCF 7 (human breast cancer) cells, depicted the greater inhibition of proliferation of cells (64%) at 100 μg mL^−1.     

Polylactide-based polyurethane and its shape-memory behavior

A series of polylactide polyurethanes (PLAUs) were synthesized from poly(l-lactide) diols, hexamethylene diisocyanate (HDI), and 1,4-butanediol (BDO). Their thermal and mechanical properties and shape-memory behavior were studied by infrared spectroscopy (IR), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), tensile testing, and thermal mechanical analysis (TMA). The T_gs of these polymers were in the range of 33-53 °C, and influenced by the M_n of the PLA diol and the ratio of the soft-segment to the hard-segment. These materials can restore their shapes almost completely after 150% elongation or twofold compression. By changing the M_n of the PLA diol and the ratio of the hard-to-soft-segment, their T_gs and shape-recovery temperatures can be adjusted to the neighborhood of the body temperature. Therefore, these PLAUs are expected to find practical medical applications.     

Transverse fluctuation analysis of single extended DNA molecules

We observed fluctuations of elongated DNA molecules by fluorescence microscopy. The molecules are fixed at both ends and undulate. Mode analysis of the thermally excited undulations of the labeled DNA molecules gives access to the spectral density of the amplitude fluctuations. From these measurements we estimate the tension acting on the DNA molecules. We found the forces to be within the entropic elasticity range of a typical DNA molecule (measured on the single-molecule level). Received: 11 November 2002 / Accepted: 12 May 2002 / Published online: 4 June 2003 RID="a" ID="a"Present address: Center for Studies in Physics and Biology, Rockefeller University, 1230 York Avenue, New York, NY 10021, USA. e-mail: zoherg@rockefeller.edu     

Natural-based plasticizers and biopolymer films: A review

In recent years, much attention has been focused on research to replace petroleum-based commodity plastics, in a cost-effective manner, with biodegradable materials offering competitive mechanical properties. Biopolymers have been considered as the most promising materials for this purpose. However, they generally present poor mechanical properties regarding processability and end-use application, since the fragility and brittleness exhibited during thermoformation can limit their potential for application. In order to overcome this problem, plasticizers are added to provide the necessary workability to biopolymers. This class of products became more visible when biodegradable additives and plasticizers also became the focus of material scientists. The use of natural and/or biodegradable plasticizers, with low toxicity and good compatibility with several plastics, resins, rubber and elastomers in substitution of conventional plasticizers, such as phthalates and other synthetic conventional plasticizers attracted the market along with the increasing worldwide trend towards use of biopolymers. Here we discuss the main results and developments in natural plasticizer/synthetic and biopolymer-based films during the last decades.     

Evaluation of a Gelatin-Modified Poly(ε-Caprolactone) Film as a Scaffold for Lung Disease

Lung transplantation is a necessary step for the patients with the end stage of chronic obstructive pulmonary disease. The use of artificial lungs is a promising alternative to natural lung transplantation which is complicated and is restricted by low organ donations. For successful lung engineering, it is important to choose the correct combination of specific biological cells and a synthetic carrier polymer. The focus of this study was to investigate the interactions of human lung epithelial cell line NCl-H292 that is involved in lung tissue development with the biodegradable poly(ε-caprolactone) before and after its chemical modification to evaluate potential for use in artificial lung formation. Also, the effect of polymer chemical modification on its mechanical and surface properties has been investigated. The poly(ε-caprolactone) surface was modified using aminolysis followed by immobilization of gelatin. The unmodified and modified polymer surfaces were characterized for roughness, tensile strength, and NCl-H292 metabolic cell activity. The results showed for the first time the possibility for NCI-H292 cells to adhere on this polymeric material. The resazurin assay showed that the metabolic activity at 24?h postseeding of 80% in the presence of the unmodified and greater than 100% in the presence of the modified polymer was observed. The roughness of the poly(ε-caprolactone) increased from 4 to 26?nm and the film strength increased from 0.01 to 0.045 kN when the material was chemically modified. The results obtained to date show potential for using modified poly(ε-caprolactone) as a scaffold for lung tissue engineering.