Examining the physico-chemical, structural and thermo-mechanical properties of naturally occurring Acacia pennata fibres treated with KMnO4

Natural fiber is a viable and possible option when looking for a material with high specific strength and high specific modulus that is lightweight, affordable, biodegradable, recyclable, and eco-friendly to reinforce polymer composites. There are many methods in which natural fibres can be incorporated into composite materials. The purpose of this research was to evaluate the physico-chemical, structural, thermal, and mechanical properties of Acacia pennata fibres (APFs). Scanning electron microscopy was used to determine the AP fibers' diameter and surface shape. The crystallinity index (64.47%) was discovered by XRD. The irregular arrangement and rough surface are seen in SEM photos. The findings demonstrated that fiber has high levels of cellulose (55.4%), hemicellulose (13.3%), and low levels of lignin (17.75%), which were determined through chemical analysis and validated by Fourier Transform Infrared Spectroscopy (FTIR). By using FTIR, the functional groups of the isolated AP fibers were examined, and TG analysis was used to look into the thermal degrading behaviour of the fibers treated with potassium permanganate (KMnO4) Due to their low density (520 kg/m3) and high cellulose content (55.4%), they have excellent bonding qualities. Additionally, tensile tests were used for mechanical characterisation to assess their tensile strength (685 MPa) and elongation.

Green chemical and hybrid enzymatic pretreatments for lignocellulosic biorefineries: Mechanism and challenges

The greener chemical and enzymatic pretreatments for lignocellulosic biomasses are portraying a crucial role owing to their recalcitrant nature. Traditional pretreatments lead to partial degradation of lignin and hemicellulose moieties from the pretreated biomass. But it still restricts the enzyme accessibility for the digestibility towards the celluloses and the interaction of lignin-enzymes, nonproductively. Moreover, incursion of certain special chemical treatments and other lignin sulfonation techniques to the enzymatic pretreatment (hybrid enzymatic pretreatment) enhances the lignin structural modification, solubilization of the hemicelluloses and both saccharification and fermentation processes (SAF). This article concentrates on recent developments in various chemical and hybrid enzymatic pretreatments on biomass materials with their mode of activities. Furthermore, the issues on strategies of the existing pretreatments towards their industrial applications are highlighted, which could lead to innovative ideas to overcome the challenges and give guideline for the researchers towards the lignocellulosic biorefineries.

Are excess carbohydrates the main link to diabetes & its complications in Asians?

Dietary carbohydrates form the major source of energy in Asian diets. The carbohydrate quantity and quality play a vital function in the prevention and management of diabetes. High glycaemic index foods elicit higher glycaemic and insulinaemic responses and promote insulin resistance and type 2 diabetes (T2D) through beta-cell exhaustion. This article reviews the evidence associating dietary carbohydrates to the prevalence and incidence of T2D and metabolic syndrome (MS) in control of diabetes and their role in the complications of diabetes. Cross-sectional and longitudinal studies show that higher carbohydrate diets are linked to higher prevalence and incidence of T2D. However, the association seems to be stronger in Asian-Indians consuming diets high in carbohydrates and more marked on a background of obesity. There is also evidence for high carbohydrate diets and risk for MS and cardiovascular disease (CVD). However, the quality of carbohydrates is also equally important. Complex carbohydrates such as brown rice, whole wheat bread, legumes, pulses and green leafy vegetables are good carbs. Conversely, highly polished rice or refined wheat, sugar, glucose, highly processed foods such as cookies and pastries, fruit juice and sweetened beverages and fried potatoes or French fries are obviously ‘bad’ carbs. Ultimately, it is all a matter of balance and moderation in diet. For Indians who currently consume about 65-75 per cent of calories from carbohydrates, reducing this to 50-55 per cent and adding enough protein (20-25%) especially from vegetable sources and the rest from fat (20-30%) by including monounsaturated fats (e.g. groundnut or mustard oil, nuts and seeds) along with a plenty of green leafy vegetables, would be the best diet prescription for the prevention and management of non-communicable diseases such as T2D and CVD.

Theoretical, photophysical and biological investigations of an organic charge transfer compound 2-aminobenzimidazolium-2-oxyisoindolate-1,3-dione-2-hydroxyisoindoline-1,3-dione

The synthesized charge transfer compound exhibits excellent non-linear optical and biological properties.

Synthesis, characterization, biological evaluation and docking studies of macrocyclic binuclear manganese(II) complexes containing 3,5-dinitrobenzoyl pendant arms

A series of bis(phenoxo) bridged binuclear manganese(II) complexes of the type [Mn2L(1-3)](ClO4)2 (1-3) containing 3,5-dinitrobenzoyl pendant-arms have been synthesized by cyclocondensation of 2,6-diformyl-4-R-phenols (where R=CH3, C(CH3)3 or Br) with 2,2'-3,5-dinitrobenzoyliminodi(ethylamine) trihydrochloride in the presence of manganese(II) perchlorate. The IR spectra of complexes indicate the presence of uncoordinated perchlorate anions. The UV-Vis spectra of complexes suggest the distorted octahedral geometry around manganese(II) nuclei. The EPR spectra of Mn(II) complexes show a broad signal with g value 2.03-2.04, which is characteristic for octahedral high spin Mn(2+) complex. The observed room temperature magnetic moment values of the Mn(II) complexes (5.60-5.62B.M.) are less than the normal value (5.92B.M.), indicating weak antiferromagnetic coupling interaction between the two metal ions. Electrochemical studies of the complexes show two distinct quasi-reversible one electron transfer processes in the cathodic (E(1)pc=-0.73 to -0.76V, E(2)pc=-1.30 to -1.36V), and anodic (E(1)pa=1.02-1.11V, E(2)pa=1.32-1.79V) potential regions. Antibacterial efficacy of complexes have been screened against four Gram (-ve) and two Gram (+ve) bacterial strains. The DNA interaction studies suggest that these complexes bind with CT-DNA by intercalation, giving the binding affinity in the order 1>2>3. All the complexes display significant cleavage activity against circular plasmid pBR322 DNA. Docking simulation was performed to insert complexes into the crystal structure of EGFR tyrosine kinase and B-DNA at active site to determine the probable binding mode.

Finger millet (Ragi, Eleusine coracana L.): a review of its nutritional properties, processing, and plausible health benefits

Finger millet or ragi is one of the ancient millets in India (2300 BC), and this review focuses on its antiquity, consumption, nutrient composition, processing, and health benefits. Of all the cereals and millets, finger millet has the highest amount of calcium (344mg%) and potassium (408mg%). It has higher dietary fiber, minerals, and sulfur containing amino acids compared to white rice, the current major staple in India. Despite finger millet's rich nutrient profile, recent studies indicate lower consumption of millets in general by urban Indians. Finger millet is processed by milling, malting, fermentation, popping, and decortication. Noodles, vermicilli, pasta, Indian sweet (halwa) mixes, papads, soups, and bakery products from finger millet are also emerging. In vitro and in vivo (animal) studies indicated the blood glucose lowering, cholesterol lowering, antiulcerative, wound healing properties, etc., of finger millet. However, appropriate intervention or randomized clinical trials are lacking on these health effects. Glycemic index (GI) studies on finger millet preparations indicate low to high values, but most of the studies were conducted with outdated methodology. Hence, appropriate GI testing of finger millet preparations and short- and long-term human intervention trials may be helpful to establish evidence-based health benefits.

Nutritional and sensory profile of two Indian rice varieties with different degrees of polishing

Traditional hand-pounded rice has been replaced today with highly polished white rice in the Asian Indian diets. The study aimed to evaluate the nutritional as well as the sensory differences between the brown (0% polish) and the rice milled to different degrees of polish (2.3, 4.4 and 8.0%). Bapatla and Uma (red pigmented) varieties in both raw and parboiled forms were used. The protein, fat, dietary fibre, γ-oryzanol, polyphenols, vitamin E, total antioxidant activity and free radical scavenging abilities of the brown rice decreased while the available carbohydrates increased with polishing. Sensory attributes of the cooked rice samples (whiteness, grain intactness, fluffiness, firmness, stickiness, chewiness and the cooked rice aroma) were evaluated by trained panelists. Scores for branny taste and chewiness decreased with polishing. On the whole, brown rice of both the varieties was readily accepted by the well-informed sensory trained panelists.

Glycaemic index of three Indian rice varieties

Three commonly consumed Indian rice varieties (Sona Masuri, Ponni and Surti Kolam) were tested for their glycaemic index (GI). Healthy volunteers were recruited and after an overnight fast were given a 50 g available carbohydrate portion of glucose (reference food) or different varieties of cooked rice (test foods) on separate occasions. The fasting as well as postprandial capillary blood glucose response was determined over 2 h, and the incremental area under the curve (IAUC) was calculated. The GI was calculated as the IAUC of the test food/IAUC of the reference food (glucose) × 100. The differences between the GI values for Sona Masuri (72.0 ± 4.5), Ponni (70.2 ± 3.6) and Surti Kolam (77.0 ± 4.0) rice varieties were non-significant (p = 0.606) and are all classified as high GI varieties of rice. There is an urgent need to study the GI of other commonly consumed rice varieties and to develop rice of a lower GI value.

Disseminated tuberculosis with involvement of prostate--a case report

We present a 55-year-old male who presented with painful non-healing ulcers on the lower lip and scrotum associated with productive cough, fever, anorexia and dysuria. Erythrocyte sedimentation rate was raised, sputum was positive for acid fast bacilli. Chest X-ray was suggestive of pulmonary tuberculosis. A prostate biopsy was also suggestive of tuberculosis. A diagnosis of disseminated tuberculosis was made and the patient showed a good response in two weeks.

Effects of glycine substitutions on the structure and function of gramicidin a channels

Tryptophan residues often are found at the lipid-aqueous interface region of membrane-spanning proteins, including ion channels, where they are thought to be important determinants of protein structure and function. To better understand how Trp residues modulate the function of membrane-spanning channels, we have examined the effects of Trp replacements on the structure and function of gramicidin A channels. Analogues of gramicidin A in which the Trp residues at positions 9, 11, 13, and 15 were sequentially replaced with Gly were synthesized, and the three-dimensional structure of each analogue was determined using a combination of two-dimensional NMR techniques and distance geometry-simulated annealing structure calculations. Though Trp --> Gly substitutions destabilize the beta6.3-helical gA channel structure, it is possible to determine the structure of analogues with Trp --> Gly substitutions at positions 11, 13, and 15, but not for the analogue with the Trp --> Gly substitution at position 9. The Gly11-, Gly13-, and Gly15-gA analogues form channels that adopt a backbone fold identical to that of native gramicidin A, with only small changes in the side chain conformations of the unsubstituted residues. Single-channel current measurements show that the channel function and lifetime of the analogues are significantly affected by the Trp --> Gly replacements. The conductance variations appear to be caused by sequential removal of the Trp dipoles, which alter the ion-dipole interactions that modulate ion movement. The lifetime variations did not appear to follow a clear pattern.

The structure, cation binding, transport, and conductance of Gly15-gramicidin A incorporated into SDS micelles and PC/PG vesicles

To further investigate the effect of single amino acid substitution on the structure and function of the gramicidin channel, an analogue of gramicidin A (GA) has been synthesized in which Trp(15) is replaced by Gly in the critical aqueous interface and cation binding region. The structure of Gly(15)-GA incorporated into SDS micelles has been determined using a combination of 2D-NMR spectroscopy and molecular modeling. Like the parent GA, Gly(15)-GA forms a dimeric channel composed of two single-stranded, right-handed beta(6.3)-helices joined by hydrogen bonds between their N-termini. The replacement of Trp(15) by Gly does not have a significant effect on backbone structure or side chain conformations with the exception of Trp(11) in which the indole ring is rotated away from the channel axis. Measurement of the equilibrium binding constants and Delta G for the binding of monovalent cations to GA and Gly(15)-GA channels incorporated into PC vesicles using (205)Tl NMR spectroscopy shows that monovalent cations bind much more weakly to the Gly(15)-GA channel entrance than to GA channels. Utilizing the magnetization inversion transfer NMR technique, the transport of Na(+) ions through GA and Gly(15)-GA channels incorporated into PC/PG vesicles has been investigated. The Gly(15) substitution produces an increase in the activation enthalpy of transport and thus a significant decrease in the transport rate of the Na(+) ion is observed. The single-channel appearances show that the conducting channels have a single, well-defined structure. Consistent with the NMR results, the single-channel conductances are reduced by 30% and the lifetimes by 70%. It is concluded that the decrease in cation binding, transport, and conductance in Gly(15)-GA results from the removal of the Trp(15) dipole and, to a lesser extent, the change in orientation of Trp(11).

Design and characterization of gramicidin channels with side chain or backbone mutations

Mutations and chemical substitutions of amino acid side chains and backbone atoms have proved vital for understanding the folding, structure and function of gramicidin channels in phospholipid membranes. The channel's pore is lined by peptide backbone groups; their importance for channel structure and function is shown by a single amide-to-ester replacement within the backbone, which greatly reduces the resulting channel conductance and lifetime. The four tryptophans and the intervening leucines together govern the formation and dissociation of conducting channels from single-stranded subunits. Conducting double-stranded gramicidin conformations (channels) occur rarely in membranes--except when the sequence has been altered to permit special arrangements of tryptophans or (infrequently) in unusually thick membranes. The tryptophans anchor the single-stranded channels to the membrane/solution interface, and the indole dipoles promote cation transport through the channels. Removal of any indole dipole reduces ion conductance; whereas 5-fluorination of an indole, which increases its dipole moment, enhances ion conductance. Some sequence changes at the formyl-NH-terminus (in the membrane interior, away from the tryptophans), including fluorination of the formyl-NH-terminal valine, introduce voltage-dependent channel gating. Gramicidin channels are not just static conductors, but also dynamic entities whose structure and function can be manipulated by backbone and side chain modifications.

Design and characterization of gramicidin channels

This article summarizes methods for the chemical synthesis and biophysical characterization of gramicidins with varying sequences and labels. The family of gramicidin channels has developed into a powerful model system for understanding fundamental properties, interactions, and dynamics of proteins and lipids generally, and ion channels specifically, in biological membranes.

Peptide backbone chemistry and membrane channel function: effects of a single amide-to-ester replacement on gramicidin channel structure and function

To examine the structural and functional importance of backbone amide groups in ion channels for subunit folding, hydrogen bonding, ion solvation, and ion permeation, we replaced the peptide bond between Val(1) and Gly(2) in gramicidin A by an ester bond. The substitution is at the junction between the two channel subunits, where it removes an intramolecular hydrogen bond between the NH of Gly(2) and the C==O of Val(7) and perturbs an intermolecular hydrogen bond between the C==O of Val(1) in one subunit and the NH of Ala(5) in the other subunit. The substitution thus perturbs not only subunit folding but also dimer assembly, in addition to any effects on ion permeation. This backbone modification has large effects on channel function: It alters channel stability, as monitored by the channel forming ability and channel lifetime, and ion permeability, as monitored by changes in single-channel conductance and cation permeability ratios. In fact, the homodimeric channels, with two ester-containing subunits, have lifetimes so short that it becomes impossible to characterize them in any detail. The peptide --> ester substitution, however, does not affect the basic subunit fold because heterodimeric channels can form between a subunit with an ester bond and a native subunit. These heterodimeric channels, with only a single ester bond, are more easily characterized; the lone ester reduces the single-channel conductance about 4-fold and the lifetime about 200-fold as compared to the native homodimeric channels. The altered channel function results from a perturbation/disruption of the hydrogen bond network that stabilizes the backbone, as well as the membrane-spanning dimer, and that forms the lining of the ion-conducting pore. Molecular dynamics simulations show the expected destabilization of the modified heterodimeric or homodimeric channels, but the changes in backbone structure and dynamics are remarkably small. The ester bond is somewhat unstable, which precluded further structural characterization. The lability also led to a hydrolysis product that terminates with an alcohol and lacks formyl-Val. Symmetric channels formed by the hydrolyzed product again have short lifetimes, but the channels are distinctly different from those formed by the ester gramicidin A. Furthermore, well-behaved asymmetric channels form between the hydrolysis product and reference subunits that have either an L- or a D-residue at the formyl-NH-terminus.

Antioxidant activity of selected Indian spices

Spices and vegetables possess antioxidant activity that can be applied for preservation of lipids and reduce lipid peroxidation in biological systems. The potential antioxidant activities of selected spices extracts (water and alcohol 1:1) were investigated on enzymatic lipid peroxidation. Water and alcoholic extract (1:1) of commonly used spices (garlic, ginger, onion, mint, cloves, cinnamon and pepper) dose-dependently inhibited oxidation of fatty acid, linoleic acid in presence of soybean lipoxygenase. Among the spices tested, cloves exhibited highest while onion showed least antioxidant activity. The relative antioxidant activities decreased in the order of cloves, cinnamon, pepper, ginger, garlic, mint and onion. Spice mix namely ginger, onion and garlic; onion and ginger; ginger and garlic showed cumulative inhibition of lipid peroxidation thus exhibiting their synergistic antioxidant activity. The antioxidant activity of spice extracts were retained even after boiling for 30 min at 100 degrees C, indicating that the spice constituents were resistant to thermal denaturation. The antioxidant activity of these dietary spices suggest that in addition to imparting flavor to the food, they possess potential health benefits by inhibiting the lipid peroxidation.

Conformational study of valinomycin: a molecular dynamics approach

Valinomycin is a highly flexible cyclic dodecadepsipeptide that transports ions across membranes. Such a flexibility in the conformation is required for its biological function since it has to encounter a variety of environments and liganding state. Exploration of conformational space of this molecule is therefore important and is one of the objectives of the present study that has been carried out by means of high temperature Molecular Dynamics. Further, the stability of the known bracelet-like structure of the uncomplexed valinomycin and the inherent flexibility around this structure has been investigated. The uncomplexed form of valinomycin has been simulated at 75-100 K for 1 ns in order to elucidate the average conformational properties. An alanine-analog of valinomycin has been simulated under identical conditions in order to evaluate the effect of sidechain on the conformational properties, The studies confirm the effect of sidechain on conformational equilibrium.

Effect of constraints by threonine on proline containing alpha-helix--a molecular dynamics approach

Proline plays an important role in the secondary structure of proteins. In the pursuit of understanding its structural role, Proline containing helices with constraints have been studied by employing molecular dynamics (MD) technique. In the present study, the constraint introduced is a threonine residue, whose sidechain has intramolecular hydrogen bond interaction with the backbone oxygen atom. The three systems that have been chosen for characterization are: (1) Ace-(Ala)12-Thr-Pro-(Ala)10-NHMe, (2) Ace-(Ala)13-Pro-Ala-Thr-(Ala)8-NHMe and (3) Ace-(Ala)13-Pro-(Ala)3-Thr-(Ala)6-NHMe. The equilibrium structures and structural transitions have been identified by monitoring the backbone dihedral angles, bend related parameters and the hydrogen bond interactions. The MD averages and root mean square (r.m.s.) fluctuations are compared and discussed. Energy minimization has been carried out on selected MD simulated points in order to analyze the characteristics of different conformations.

Structure of valinomycin by molecular dynamics studies

Valinomycin is an important ionophore which exhibits a high conformational flexibility. The study of various conformations adopted by this molecule together with the study of flexibility in a given conformation can throw light on the ion transport by the ionophore across the membrane. Molecular dynamics (MD) studies are ideal to characterize the flexibility in different parts of the molecule and can also give an idea of various conformations adopted by the molecule at a given temperature. Hence MD studies at 100K have been carried out on the minimized crystal structure of the molecule to scan the possible conformations in the neighbourhood of the well known 'bracelet' like structure of uncomplexed Valinomycin, Properties, like the flexibility, average values, r.m.s. fluctuations of the various intramolecular hydrogen bonds are discussed. Energy minimization has been carried out on selected MD simulated points to analyze the characteristics of the unique conformation adopted by this molecule at this temperature.