Application of poly ethylene glycol hydrogel to overcome latex urinary catheter related problems

Urinary catheterization is a routine procedure in an intensive care unit (ICU) for monitoring the urine output of critically ill patients. The catheters which are most often used to help with urinary incontinence and retention also face problems like blockage, leakage and infection. These problems are due to proteins that adhere to the catheter surface and quickly build up on each other forming a protein layer. As the layers build up they can crystallize, providing the major source of blockage and leakage. Current strategies to avoid these problems include coating a catheter with silver alloy to reduce bacteria on the catheter surface. However, silver alloy coatings can lead to increased silver resistance for bacteria. Since silver is already used as an antibacterial agent in many places in a hospital, it is even more possible that resistance can develop. An alternative solution is presented involving coating latex, a common urinary catheter material with a micro layer (5-100 microns) of polyethylene glycol. This hydrogel is applied using an interfacial photopolymerization process with ethyl eosin as the photoinitiator. A 25 ppm concentration of ethyl eosin provided the strongest gel to surface adhesion and significantly lowered protein adhesion when compared to an uncoated latex substrate.     

In Vivo Studies in Rhodospirillum rubrum Indicate That Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (Rubisco) Catalyzes Two Obligatorily Required and Physiologically Significant Reactions for Distinct Carbon and Sulfur Metabolic Pathways

All organisms possess fundamental metabolic pathways to ensure that needed carbon and sulfur compounds are provided to the cell in the proper chemical form and oxidation state. For most organisms capable of using CO₂ as sole source of carbon, ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) catalyzes primary carbon dioxide assimilation. In addition, sulfur salvage pathways are necessary to ensure that key sulfur-containing compounds are both available and, where necessary, detoxified in the cell. Using knock-out mutations and metabolomics in the bacterium Rhodospirillum rubrum, we show here that Rubisco concurrently catalyzes key and essential reactions for seemingly unrelated but physiologically essential central carbon and sulfur salvage metabolic pathways of the cell. In this study, complementation and mutagenesis studies indicated that representatives of all known extant functional Rubisco forms found in nature are capable of simultaneously catalyzing reactions required for both CO₂-dependent growth as well as growth using 5-methylthioadenosine as sole sulfur source under anaerobic photosynthetic conditions. Moreover, specific inactivation of the CO₂ fixation reaction did not affect the ability of Rubisco to support anaerobic 5-methylthioadenosine metabolism, suggesting that the active site of Rubisco has evolved to ensure that this enzyme maintains both key functions. Thus, despite the coevolution of both functions, the active site of this protein may be differentially modified to affect only one of its key functions.     

The influence of sunlight on the localized corrosion of UNS S31600 in natural seawater

Tests were conducted on the performance of UNS S31600 stainless steel (SS) in a natural day/night cycle vs full darkness under conditions of natural marine biofilm accumulation. In quiescent flowing seawater tests in the laboratory as well as under natural immersion in the sea, diffuse sunlight (～10% of natural) counteracted the influence of marine biofilms and produced substantial inhibition of the corrosion of SS. Thus, the probabilities (percentage attack) and propagation rates (depths of attack) in multiple crevice tests were substantially lower in the day/night cycle than in the dark. A benefit was also observed for welded SS in terms of the time to corrosion initiation and the mass loss. SS in the passive state showed broader passive regions, well-defined breakdown potentials and markedly smaller anodic and cathodic current densities under the diurnal cycle. The overall reduction in corrosion is attributed to a combination of electrochemical photoinhibition and simultaneous photoinactivation of microbially mediated metal redox reactions linked to cathodic kinetics. These data offer fresh insights into the behaviour of SS under practical seawater situations and the proposed potential use of illumination in the mitigation of biologically influenced consequences.     

Synthesis and screening of (E)-1-(β-D-galactopyranosyl)-4-(aryl)but-3-ene-2-one against Mycobacterium tuberculosis

A series of galactose-derived aryl enones were synthesised and screened against Mycobacterium tuberculosis H₃₇Rv. Preliminary results were promising with MIC values in the range 1.56-12.5 μg/mL.     

Learning from Gobind Khorana: “The difficult we do today,the impossible tomorrow”

Prof. Har Gobind Khorana was one of the greatest scientists of the twentieth century. Drawing on his strong roots in organic chemistry, he had a remarkable ability to select and focus his intellect on successfully addressing some of the most important challenges in modern biology in a career spanning nearly 6 decades. His pioneering contributions in gene synthesis and protein structure–function studies, and more broadly in what he termed “chemical biology,” continue to have a major impact on modern biomedical science.     

Hypothesis generation in signaling networks.

Biological signaling networks comprise the chemical processes by which cells detect and respond to changes in their environment. Such networks have been implicated in the regulation of important cellular activities, including cellular reproduction, mobility, and death. Though technological and scientific advances have facilitated the rapid accumulation of information about signaling networks, utilizing these massive information resources has become infeasible except through computational methods and computer-based tools. To date, visualization and simulation tools have received significant emphasis. In this paper, we present a graph-theoretic formalization of biological signaling network models that are in wide but informal use, and formulate two problems on the graph: the Constrained Downstream and Minimum Knockout Problems. Solutions to these problems yield qualitative tools for generating hypotheses about the networks, which can then be experimentally tested in a laboratory setting. Using established graph algorithms, we provide a solution to the Constrained Downstream Problem. We also show that the Minimum Knockout Problem is NP-Hard, propose a heuristic, and assess its performance. In tests on the Epidermal Growth Factor Receptor (EGFR) network, we find that our heuristic reports the correct solution to the problem in seconds. Source code for the implementations of both solutions is available from the authors upon request.     

Features of ribosome-peptidyl-tRNA interactions essential for tryptophan induction of tna operon expression

Certain nascent peptide sequences, when within the ribosomal exit tunnel, can inhibit translation termination and/or peptide elongation. The 24 residue leader peptidyl-tRNA of the tna operon of E. coli, TnaC-tRNA(Pro), in the presence of excess tryptophan, resists cleavage at the tnaC stop codon. TnaC residue Trp12 is crucial for this inhibition. The approximate location of Trp12 in the exit tunnel was determined by crosslinking Lys11 of TnaC-tRNA(Pro) to nucleotide A750 of 23S rRNA. Methylation of nucleotide A788 of 23S rRNA was reduced by the presence of Trp12 in TnaC-tRNA(Pro), implying A788 displacement. Inserting an adenylate at position 751, or introducing the change U2609C in 23S rRNA or the change K90H or K90W in ribosomal protein L22, virtually eliminated tryptophan induction. These modified and mutated regions are mostly located near the putative site occupied by Trp12 of TnaC-tRNA(Pro). These findings identify features of the ribosomal exit tunnel essential for tna operon induction.     

Biophysical approaches for studying the integrity and function of tight junctions

Cell-cell adhesion is an extremely important phenomenon as it influences several biologically important processes such as inflammation, cell migration, proliferation, differentiation and even cancer metastasis. Furthermore, proteins involved in cell-cell adhesion are also important from the perspective of facilitating better drug delivery across epithelia. The adhesion forces imparted by proteins involved in cell-cell adhesion have been the focus of research for sometime. However, with the advent of nanotechnological techniques such as the atomic force microscopy (AFM), we can now quantitatively probe these adhesion forces not only at the cellular but also molecular level. Here, we review the structure and function of tight junction proteins, highlighting some mechanistic studies performed to quantify the adhesion occurring between these proteins and where possible their association with human diseases. In particular, we will highlight two important experimental techniques, namely the micropipette step pressure technique and the AFM that allow us to quantify these adhesion forces at both the cellular and molecular levels, respectively.     

Protective effect of active oxygen scavengers on protein degradation and photochemical function in photosystem I submembrane fractions during light stress

The protective role of reactive oxygen scavengers against photodamage was studied in isolated photosystem (PS) I submembrane fractions illuminated (2000 microE x m(-2) x s(-1)) for various periods at 4 degrees C. The photochemical activity of the submembrane fractions measured as P700 photooxidation was significantly protected in the presence of histidine or n-propyl gallate. Chlorophyll photobleaching resulting in a decrease of absorbance and fluorescence, and a blue-shift of both absorbance and fluorescence maximum in the red region, was also greatly delayed in the presence of these scavengers. Western blot analysis revealed the light harvesting antenna complexes of PSI, Lhca2 and Lhca1, were more susceptible to strong light when compared to Lhca3 and Lhca4. The reaction-center proteins PsaB, PsaC, and PsaE were most sensitive to strong illumination while other polypeptides were less affected. Addition of histidine or n-propyl gallate lead to significant protection of reaction-center proteins as well as Lhca against strong illumination. Circular dichroism (CD) spectra revealed that the alpha-helix content decreased with increasing period of light exposure, whereas beta-strands, turns, and unordered structure increased. This unfolding was prevented with the addition of histidine or n-propyl gallate even after 10 h of strong illumination. Catalase or superoxide dismutase could not minimize the alteration of PSI photochemical activity and structure due to photodamage. The specific action of histidine and n-propyl gallate indicates that 1O2 was the main form of reactive oxygen species responsible for strong light-induced damage in PSI submembrane fractions.