Values of the kinetic parameters <i>n</i> and rate constant <i>k</i>, for fibrillation of BSA in the absence and presence 0.05 M, 0.10 M, 0.25 M, 0.50 M and 1.00 M of 4-hydroxy-trans-L-proline (HPro), sorbitol (Sorb), sarcosine (Sarc), proline (Pro), and glycine betaine (GB) at pH 7.4 and 333.15 K.

<p>Values of the kinetic parameters <i>n</i> and rate constant <i>k</i>, for fibrillation of BSA in the absence and presence 0.05 M, 0.10 M, 0.25 M, 0.50 M and 1.00 M of 4-hydroxy-trans-L-proline (HPro), sorbitol (Sorb), sarcosine (Sarc), proline (Pro), and glycine betaine (GB) at pH 7.4 and 333.15 K.</p

Selective inhibition of aggregation/fibrillation of bovine serum albumin by osmolytes: Mechanistic and energetics insights

<div><p>Bovine serum albumin (BSA) is an important transport protein of the blood and its aggregation/fibrillation would adversely affect its transport ability leading to metabolic disorder. Therefore, understanding the mechanism of fibrillation/aggregation of BSA and design of suitable inhibitor molecules for stabilizing its native conformation, are of utmost importance. The qualitative and quantitative aspects of the effect of osmolytes (proline, hydroxyproline, glycine betaine, sarcosine and sorbitol) on heat induced aggregation/fibrillation of BSA at physiological pH (pH 7.4) have been studied employing a combination of fluorescence spectroscopy, Rayleigh scattering, isothermal titration calorimetry (ITC), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Formation of fibrils by BSA under the given conditions was confirmed from increase in fluorescence emission intensities of Thioflavin T over a time period of 600 minutes and TEM images. Absence of change in fluorescence emission intensities of 8-Anilinonaphthalene-1-sulfonic acid (ANS) in presence of native and aggregated BSA signify the absence of any amorphous aggregates. ITC results have provided important insights on the energetics of interaction of these osmolytes with different stages of the fibrillar aggregates of BSA, thereby suggesting the possible modes/mechanism of inhibition of BSA fibrillation by these osmolytes. The heats of interaction of the osmolytes with different stages of fibrillation of BSA do not follow a trend, suggesting that the interactions of stages of BSA aggregates are osmolyte specific. Among the osmolytes used here, we found glycine betaine to be supporting and promoting the aggregation process while hydroxyproline to be maximally efficient in suppressing the fibrillation process of BSA, followed by sorbitol, sarcosine and proline in the following order of their decreasing potency: Hydroxyproline> Sorbitol> Sarcosine> Proline> Glycine betaine.</p></div

ITC profiles for the titrations of lysozyme solution at saturation stage (after 90 h of incubation) with (A) L-proline (B) 4-hydroxy-L-proline and (C) sarcosine at 25°C.

<p>ITC profiles for the titrations of lysozyme solution at saturation stage (after 90 h of incubation) with (A) L-proline (B) 4-hydroxy-L-proline and (C) sarcosine at 25°C.</p

Establishing Structure Property Relationship in Drug Partitioning into and Release from Niosomes: Physical Chemistry Insights with Anti-Inflammatory Drugs

Understanding the physical chemistry underlying interactions of drugs with delivery formulations is extremely important in devising effective drug delivery systems. The partitioning and release kinetics of diclofenac sodium and naproxen from Brij 30 and Triton X-100 niosomal formulations have been addressed based on structural characterization, partitioning energetics, and release kinetics, thus establishing a relationship between structures and observed properties. Both the drugs partition in nonpolar regions of TX-100 niosomes via stacking of aromatic rings. The combined effects of interactions of the drugs with polar head groups and the rigidity of the niosome vesicles determine entry and partitioning of drugs into niosomes. The observed slower rate of release of the drugs from the drug encapsulated niosomes of TX-100 than those of Brij 30, suggest stable complexation of drugs in the nonpolar interior of the former. No release of drugs from the niosomes was observed until 24 h even upon varying pH conditions without SDS. However, SDS in drug loaded niosomes led to release of drugs in as early as 6 h. The sustained pattern of in vitro release kinetics of the drugs thus observed from our niosomal preparations suggest these vesicular systems to be promising for pharamaceutical applications as potential drug delivery vehicles

Limiting standard enthalpies (Δ<i>H</i>°) of interaction (in kJ mol^-1) of the different stages of BSA aggregates with 0.50 M concentration of hydroxyproline, sorbitol, sarcosine, proline and glycine betaine.

<p>Limiting standard enthalpies (Δ<i>H</i>°) of interaction (in kJ mol^-1) of the different stages of BSA aggregates with 0.50 M concentration of hydroxyproline, sorbitol, sarcosine, proline and glycine betaine.</p

ThT binding assay in the presence of osmolytes.

<p>Kinetics of BSA fibrillation in the absence and in the presence of 0.05 M, 0.10 M, 0.25 M, 0.50 M and 1.00 M of osmolytes (A) 4-hydroxy-L-proline (HPro) and (B) Glycine Betaine (GB) monitored from the changes in fluorescence emission intensity of ThT as a function of time.</p

Isothermal Titration Calorimetry (ITC) experiments.

<p>Representative ITC profile for the titration of stages (1 to 3) of BSA aggregates into 0.50 M of (A) hydroxyproline (HPro) and (B) glycine betaine (GB).</p

Thermal denaturation of BSA and temperature dependent kinetics of BSA fibrillation.

<p>(A) Representative plot of absorbance versus wavelength for thermal denaturation of 15.06 μM BSA and (B) Temperature dependent kinetics of 75.30 μM BSA fibrillation monitored from ThT fluorescence emission at pH 7.4.</p

DSC scans of 10 mg ml⁻¹ lysozyme (A) at the different stages of fibrillization process: line A represents only buffer, B represents for naïve lysozyme, line C represents for nucleation phase after 48 h of incubation, line D represents for elongation period after 61 h of incubation and line E represents for saturation phase after 90 h of incubation and (B) showing change in heat capacity at the different stages of fibrillization process: line N represents C_p for native stage, line E represents C_p for elongated stage and line S represents C_p for saturation stage.

<p>DSC scans of 10 mg ml⁻¹ lysozyme (A) at the different stages of fibrillization process: line A represents only buffer, B represents for naïve lysozyme, line C represents for nucleation phase after 48 h of incubation, line D represents for elongation period after 61 h of incubation and line E represents for saturation phase after 90 h of incubation and (B) showing change in heat capacity at the different stages of fibrillization process: line N represents C_p for native stage, line E represents C_p for elongated stage and line S represents C_p for saturation stage.</p

ITC profiles for the titrations of lysozyme at nucleation stage (after 48 h of incubation) with (A) L-proline (B) 4-hydroxy-L-proline and (C) sarcosine at 25°C.

<p>ITC profiles for the titrations of lysozyme at nucleation stage (after 48 h of incubation) with (A) L-proline (B) 4-hydroxy-L-proline and (C) sarcosine at 25°C.</p