Sharadwata Pan

Universal solvent quality crossover of the zero shear rate viscosity of semidilute DNA solutions

The scaling behavior of the zero shear rate viscosity of semidilute unentangled Deoxyribonucleic acid (DNA) solutions, in the double crossover regime driven by temperature and concentration, is mapped out by systematic experiments. The viscosity is shown to have a power law dependence on the scaled concentration c/c*, with an effective exponent that depends on the solvent quality parameter z. The determination of the form of this universal crossover scaling function requires the estimation of the θ-temperature of dilute DNA solutions in the presence of excess salt, and the determination of the solvent quality parameter at any given molecular weight and temperature. The θ-temperature is determined to be Tθ ≈ 15 °C using static light scattering, and the solvent quality parameter has been determined by dynamic light scattering.

Antioxidative peptides derived from food proteins

The search for natural antioxidants is an ongoing endeavour as an aid to combat the harmful effects of free radicals. Research advances in the past few decades have shown that, by controlled enzymatic hydrolysis, natural antioxidants can be produced from food proteins. In this chapter, the role of certain antioxidative peptides derived from food proteins is discussed in relation to their prospect in the prevention of oxidative stress. The molecular diversity of these food peptides is described together with their pharmacological effects and mechanisms of action in relation to antioxidation. The production of these peptides and the elucidation of their antioxidative peptides are also presented. Owing to their therapeutic potential, antioxidative peptides derived from food proteins can be incorporated as ingredients in functional foods, nutraceuticals and pharmaceuticals, where their biological activities may inhibit product oxidation or assist in the control and prevention of diseases induced by free radicals. However, further insightful research is needed to overcome certain scientific challenges and thereby increase and promote consumer acceptance of these natural antioxidants.

A Proposal for a Quality System for Herbal Products

Today, there is an increasing worldwide demand for botanicals. Developing countries heavily rely on plant-derived medicines for their primary healthcare. One reason amongst many is the relatively inexpensive process economics and the lack of stringent product governance associated with the exploitation of traditional plant medicines compared with modern medicine. Developed countries impose stringent good manufacturing practices and quality control measures on drug products derived from any manufacturing process, regardless of the primary raw material. However, several factors hamper the full-scale application of traditional plant medicines: lack of implementation of effective quality assurance in the manufacturing process; lack of traceability in the supply chain and associated value additions; and inefficient identification of molecular species that affect the therapeutic efficacy of the final product. There lacks an assessable, causative, and prognostic relationship between the raw materials, the manufacturing process and the final product quality. This article suggests some solutions that may be adopted by the phytodrug industry to widen its global reach and retain its credibility. Primarily among them is the implementation of hazards analysis and critical control point in the manufacturing process and employment of process analytical technology for ensuring minimal deviation from the manufacturing process of phytotherapeutics.

Viscosity radius of polymers in dilute solutions: Universal behavior from DNA rheology and brownian dynamics simulations

The swelling of the viscosity radius, αη, and the universal viscosity ratio, UηR, have been determined experimentally for linear DNA molecules in dilute solutions with excess salt, and numerically by Brownian dynamics simulations, as a function of the solvent quality. In the latter instance, asymptotic parameter free predictions have been obtained by extrapolating simulation data for finite chains to the long chain limit. Experiments and simulations show a universal crossover for αη and UηR from θ to good solvents in line with earlier observations on synthetic polymer− solvent systems. The significant difference between the swelling of the dynamic viscosity radius from the observed swelling of the static radius of gyration is shown to arise from the presence of hydrodynamic interactions in the nondraining limit. Simulated values of αη and UηR are in good agreement with experimental measurements in synthetic polymer solutions reported previously and with the measurements in linear DNA solutions reported here.

Cell Surface Display

The manipulation of the cell surfaces of prokaryotes (mainly bacteria) and eukaryotes (such as Yeast) has manifested to be an area of stupendous ongoing research, with intelligent widespread applications spanning different arenas of biological sciences (Charbit et al., 1988; Cruz et al., 2000; Francisco et al., 1993; Gotz, 1990; Jostock & Dubel, 2005; Keskinkan et al., 2004; Kotrba et al., 1999; Lee & Schnaitman, 1980; Liljeqvist et al., 1997; Martineau et al., 1991; Mizuno et al., 1983; Sousa et al., 1996; Taschner et al., 2002; Wernerus & Stahl, 2004; Willett et al., 1995; Xu & Lee, 1999). Till date, majority of the surface display systems developed for Gram-negative bacteria involve introducing external peptides into surface-approachable loops of naturally displayed proteins. This sometimes put extreme size restrictions on the displayed components (Wernerus & Stahl, 2004). However, this problem is more or less resolved since larger proteins could be inserted through some recently developed bacterial display systems for Gram-negative bacteria (Charbit et al., 1988; Cruz et al., 2000; Lee & Schnaitman, 1980; Mizuno et al., 1983; Xu & Lee, 1999). Thanks to some tireless research, it is now evident that the structural properties of the cell wall in Gram-positive bacteria, i.e. the thick peptidoglycan layer, make them suitable candidates for strict laboratory procedures and demanding field applications (Jostock & Dubel, 2005). On the other hand, lower transformation efficiency has been a significant disadvantage of using Gram-positive bacteria (Wernerus & Stahl, 2004), considering if someone is working with surface-displayed conjunctional libraries for affinity-based selections. However, libraries of significant size could also be obtained for Gram-positive bacteria. Transformation frequencies as high as 105 − 106 colony forming units/μg of DNA have been observed for Staphylococcus carnosus (Gotz, 1990). Until recently, different surface displaying systems have been successfully developed (Lee et al., 2003). Based on their recombinant portfolios, these can be categorized into three principal groups: C-terminal fusion, N-terminal fusion, and Sandwich fusion. Natural occurring surface proteins with distinct restricting signals within their N-terminal part may use a C-terminal fusion mechanism to affix external peptides to the C terminus of that functional portion. In a similar way, a N-terminal fusion system points external proteins to the cell wall by using either Staphylococcus aureus protein A, fibronectin binding protein B, Streptococcus pyogenes fibrillar M protein, and Saccharomyces cerevisiae α-agglutinin, all of which contain C-terminal screening signals. However, in many surface proteins, the whole structure is an essentiality for successful aggregation, primarily because the anchoring regions are absent in their subunits (such as outer membrane proteins or OMPs). Here, the sandwich fusion plays a vital role. Escherichia coli PhoE, FimH, FliC, and PapA act as good carriers for sandwich fusion for small peptides (Xu & Lee, 1999). 4

Modern Taxonomy for Microbial Diversity

Microorganisms are actually composed of very different and taxonomically diverse groups of communities: archaea, bacteria, fungi and viruses. The members of these groups or taxa are distinct in terms of their morphology, physiology and phylogeny and fall into both prokaryotic and eukaryotic domains. They constitute a broad group of life system inhabiting the known ecosystems on earth: terrestrial and marine; including geographical locations considered to be extreme or inimical to life. The latter comprise of such areas as habitats with high salinity, alkalinity, acidity, high and low temperatures, high pressure, and high radiation. Considering the adaptability of microorganisms to grow and survive under varied physico-chemical conditions and their contribution in maintaining the balance in ecosystems, it is pertinent to catalogue their diversity as it exists. The inability to visualize them with the naked eye precludes effective classification. As such, using the available tools, microorganisms are broadly classified into prokaryotes and eukaryotes and subsequently into various taxonomical units depending on the resources available and required.

Nonlinearities and shear banding instability of polyacrylamide solutions under large amplitude oscillatory shear

The response of semidilute entangled and salt-free solutions of aqueous polyacrylamide under large amplitude oscillatory shear deformations was studied in this work. We systemically probed the effects of four polymer concentrations from 5 to 15 wt. % and two molecular weights (5–6 and 18 M) at De > 1. The mitlaos software package was utilized to analyze the nonlinear moduli, among other nonlinear parameters. We found that the polymer concentration is the dominant parameter controlling the progression into the nonlinear regime. The trends of elastic decomposition indicate an intensive strain-rate softening behavior under high strain amplitudes. At high strain rates and at higher concentrations, however, a gradual transition from shear thickening to shear thinning could be noticed for the viscous dissipation. In addition, the effect of the measuring geometry was also considered, since the rheometer was coupled with a particle image velocimetry (PIV) system in the second part of this study. The PIV results s...

Parametric Investigation of Batch Adsorption of Proteins onto Polymeric Particles.

BACKGROUND Effective bimolecular adsorption of proteins onto solid matrices is characterized by in-depth understanding of the biophysical features essential to optimize the adsorption performance. RESULTS The adsorption of bovine serum albumin (BSA) onto anion-exchange Q-sepharose solid particulate support was investigated in batch adsorption experiments. Adsorption kinetics and isotherms were developed as a function of key industrially relevant parameters such as polymer loading, stirring speed, buffer pH, protein concentration and the state of protein dispersion (solid/aqueous) in order to optimize binding performance and adsorption capacity. Experimental results showed that the first order rate constant is higher at higher stirring speed, higher polymer loading, and under alkaline conditions, with a corresponding increase in equilibrium adsorption capacity. Increasing the stirring speed and using aqueous dispersion protein system increased the adsorption rate, but the maximum protein adsorption was unaffected. Regardless of the stirring speed, the adsorption capacity of the polymer was 2.8 mg/ml. However, doubling the polymer loading increased the adsorption capacity to 9.4 mg/ml. CONCLUSIONS The result demonstrates that there exists a minimum amount of polymer loading required to achieve maximum protein adsorption capacity under specific process conditions.

Aptameric Sensing in Food Safety

Abstract Foodborne illnesses are a global menace on public health. However, because they are expensive, time-consuming, and nonspecific, standard methods used before now for detecting foodborne pathogens and biotoxins are often unsuitable for real-time detection and surveillance, particularly in low-resource communities that may serve as the source of the food basket in a geographical location. Improvements in systems for the robust detection and screening of foodborne pathogens are therefore needed to effectively regulate the transmission of foodborne pathogens by promoting early treatment and/or isolation of infected products. Interestingly, research work in bioaffinity interactions have led to advances in SELEX (systematic evolution of ligands by exponential enrichment) technology for the generation of short, single-stranded DNA/RNA molecular probes (known as aptamers) that bind selectively to specific pathogenic targets and membrane receptors. Immobilized aptamers also yields aptasensors that are effective for detection in real time. This chapter focuses on the merits and applicability of various established apta-assays over conventional techniques for the detection and screening of foodborne pathogens and biotoxins.

Bioprocessing of Functional Ingredients from Flaxseed

Flaxseeds (Linum usitatissimum L.) are oilseeds endowed with nutritional constituents such as lignans, lipids, proteins, fibre, carbohydrates, and micronutrients. Owing to their established high nutritional profile, flaxseeds have gained an established reputation as a dietary source of high value functional ingredients. Through the application of varied bioprocessing techniques, these essential constituents in flaxseeds can be made bioavailable for different applications such as nutraceuticals, cosmetics, and food industry. However, despite their food and health applications, flaxseeds contain high levels of phytotoxic compounds such as linatine, phytic acids, protease inhibitors, and cyanogenic glycosides. Epidemiological studies have shown that the consumption of these compounds can lead to poor bioavailability of essential nutrients and/or health complications. As such, these components must be removed or inactivated to physiologically undetectable limits to render flaxseeds safe for consumption. Herein, critical description of the types, characteristics, and bioprocessing of functional ingredients in flaxseed is presented.