Interaction Forces And Reaction Kinetics Of Ligand-Cell Receptor Systems Using Atomic Force Microscopy

Atomic Force Microscopy (AFM) provides superior imaging resolution and the ability to measure forces at the nanoscale. It is an important tool for studying a wide range of bio-molecular samples from proteins, DNA to living cells. We developed AFM measurement procedures to measure protein interactions on live cells at the single molecular level. These measurements can be interpreted by using proper statistical approaches and can yield important parameters about ligand-receptor interactions on live cells. However, the standard theory for analyzing rupture force data does not fit the experimental rupture force histograms. Most of the experimental measurements of rupture force data generate a probability distribution function (pdf) with a high force tail. We show that this unexpected high force tail can be attributed to multiple attachments and heterogeneous bonding by studying a model system, biotin-avidin. We have applied our methodology to the medically relevant system of discoidin domain receptors (DDR) on live cells and their interaction with their ligand, collagen. In addition, we have also used AFM to study drug-delivery particles, in particular polymer micelles containing fluorescently labeled siRNA particles. In this study, we measured interaction forces and binding probability measurements between folate receptor functionalized cantilever and different substrates, as well as combined AFM and fluorescence microscopy

Studying the spheromak rotation in data-constrained CME modelling with EUHFORIA and assessing its effect on the Bz prediction

A key challenge in space weather forecasting is accurately predicting the magnetic field topology of interplanetary coronal mass ejections (ICMEs), specifically the north-south magnetic field component (Bz) for Earth-directed CMEs. Heliospheric MHD models typically use spheromaks to represent the magnetic structure of CMEs. However, when inserted into the ambient interplanetary magnetic field, spheromaks can experience a phenomenon reminiscent of the condition known as the "spheromak tilting instability", causing its magnetic axis to rotate. From the perspective of space weather forecasting, it is crucial to understand the effect of this rotation on predicting Bz at 1 au while implementing the spheromak model for realistic event studies. In this work, we study this by modelling a CME event on 2013 April 11 using the "EUropean Heliospheric FORecasting Information Asset" (EUHFORIA). Our results show that a significant spheromak rotation up to 90 degrees has occurred by the time it reaches 1 au, while the majority of this rotation occurs below 0.3 au. This total rotation resulted in poor predicted magnetic field topology of the ICME at 1 au. To address this issue, we further investigated the influence of spheromak density on mitigating rotation. The results show that the spheromak rotation is less for higher densities. Importantly, we observe a substantial reduction in the uncertainties associated with predicting Bz when there is minimal spheromak rotation. Therefore, we conclude that spheromak rotation adversely affects Bz prediction in the analyzed event, emphasizing the need for caution when employing spheromaks in global MHD models for space weather forecasting.Comment: Accepted for publication in The Astrophysical Journal Supplement (ApJS) serie

Thermodynamic and kinetic studies on novel Platinum(II) Complex containing bidentate N,N-donor ligands in ethanol-water medium

760-767Kinetic and mechanistic investigations have been made on the displacement of the two aqua molecules from the complex 1 i.e., [Pt(2,2′-bipyridine)(H2O)2]2+ represented as {Pt(bpy)} (bpy = 2,2′-bipyridine) at pH 4.0. All the substitution reactions have been monitored at 264, 284 & 317 nm, where the spectral difference between the reactant and product is maximum. Two consecutive reaction steps have been observed for the substitution of aqua molecules with some bidentate N,N-donor ligands namely, dimethylglyoxime (L1H), 1, 2-cyclohexanedionedioxime (L2H) and α-furildioxime (L3H) in ethanol-water medium using variable-temperature and stopped-flow spectrophotometry. Among the two steps, the former is ligand dependent and the later is ligand independent, where chelation is observed. All rate and activation parameters are consistent with associative substitution mechanisms. The thermodynamic parameters have been also calculated, which gives a negative DG0 value at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex. The products of the reaction have been characterized with the help of IR and ESI-MS spectroscopic analysis

In vitro digestion of Pickering emulsions stabilized by soft whey protein microgel particles: influence of thermal treatment

Emulsions stabilized by soft whey protein microgel particles have gained research interest due to their combined advantages of biocompatibility and a high degree of resistance to coalescence. We designed Pickering oil-in-water emulsions using whey protein microgels by a facile route of heat-set gel formation followed by mechanical shear and studied the influence of heat treatment on emulsions stabilized by these particles. The aim of this study was to compare the barrier properties of the microgel particles and heat-treated fused microgel particles at the oil–water interface in delaying the digestion of the emulsified lipids using an in vitro digestion model. A combination of transmission electron microscopy and surface coverage measurements revealed an increased coverage of heat-treated microgel particles at the interface. The heat-induced microgel particle aggregation and, therefore, a fused network at the oil–water interface were more beneficial to delay the rate of digestion in the presence of pure lipase and bile salts compared to intact whey protein microgel particles, as shown by the measurements of zeta potential and free fatty acid release, plus theoretical calculations. However, simulated gastric digestion with pepsin impacted significantly on such barrier effects, due to the proteolysis of the particle network at the interface irrespective of the heat treatment, as visualized using sodium dodecyl sulfate polyacryl amide gel electrophoresis measurements

Human saliva and model saliva at bulk to adsorbed phases – similarities and differences

Human saliva, a seemingly simple aqueous fluid, is, in fact, an extraordinarily complex biocolloid that is not fully understood, despite many decades of study. Salivary lubrication is widely believed to be a signature of good oral health and is also crucial for speech, food oral processing and swallowing. However, saliva has been often neglected in food colloid research, primarily due to its high intra- to inter-individual variability and altering material properties upon collection and storage, when used as an ex vivo research material. In the last decade, colloid scientists have attempted designing model (i.e. ‘saliva mimicking fluid’) saliva formulations to understand saliva-food colloid interactions in an in vitro set up and its contribution on microstructural aspects, lubrication properties and sensory perception. In this Review, we critically examine the current state of knowledge on bulk and interfacial properties of model saliva in comparison to real human saliva and highlight how far such model salivary formulations can match the properties of real human saliva. Many, if not most, of these model saliva formulations share similarities with real human saliva in terms of biochemical compositions, including electrolytes, pH and concentrations of salivary proteins, such as α-amylase and highly glycosylated mucins. This, together with similarities between model and real saliva in terms of surface charge, has led to significant advancement in decoding colloidal interactions (bridging, depletion) of charged emulsion droplets and associated sensory perception in the oral phase. However, model saliva represents significant dissimilarity to real saliva in the lubricating properties. Based on in-depth examination of properties of mucins from animal sources (e.g. pig gastric mucins (PGM) or bovine submaxillary mucin (BSM)), we can recommend that BSM is currently the most optimal mucin source when attempting to replicate saliva based on surface adsorption and lubrication properties. Even though purification via dialysis or chromatographic techniques may influence various physicochemical properties of BSM, such as structure and surface adsorption, the lubricating properties of model saliva formulations based on BSM are generally superior and more reliable than PGM counterpart at orally relevant pH. Comparison of mucin-containing model saliva with ex vivo human salivary conditioning films suggests that mucin alone cannot replicate the lubricity of real human salivary pellicle. Mucin-based multi-layers containing mucin and oppositely charged polyelectrolytes may offer promising avenues in the future for engineering biomimetic salivary pellicle, however, this has not been explored in oral tribology experiments to date. Hence, there is a strong need for systematic studies with employment of model saliva formulations containing mucins with and without polycationic additives before a consensus on a standardized model saliva formulation can be achieved. Overall, this review provides a comprehensive framework on simulating saliva for a particular bulk or surface property when doing food oral processing experiments

Water-in-oil emulsions stabilized by surfactants, biopolymers and/or particles: A review

Background Considering the global rise of obesity and food-linked cardiovascular diseases, food industries are often challenged to produce low fat or fat-free products. Incorporation of water in the form of water-in-oil (W/O) emulsions to replace fat offers a promising strategy to address this research challenge. Scope and approach This review aims to provide succinct insights into the stabilization of W/O emulsions, focusing on interfacial design using surfactants, biopolymers, particles and/or combinations thereof that have been researched in the last decade. Particular emphasis has been given to particle (Pickering) stabilization of water droplets with bio-derived as well as non-bio-derived particles. In addition, the stabilization of W/O emulsions via viscosity modification is also briefly examined. Key findings and conclusions Although polyglycerol polyricinoleate (PGPR, E476) is considered as the ‘classic’ surfactant when it comes to stabilization of W/O emulsions, the focal point of current research has recently shifted towards the use of particle stabilizers that allow longer term stabilization against coalescence and Ostwald ripening. In particular, Pickering stabilizers that are derived from natural, biodegradable sources, such as zein, cellulose, lignin, starch and polyphenol crystals (curcumin and quercetin), with or without further modification, have attracted burgeoning attention due to the rising popularity of ‘clean-label’ products amongst consumers. Using such particles, or intelligently combining particles with biopolymers to stabilize high water volume fractions in oil continuous matrices, plus the use of biopolymers to gel the water phase, offer promising new applications in food and allied soft matter manufacturing areas in the future

Macromolecular design of folic acid functionalized amylopectin- albumin core-shell nanogels for improved physiological stability and colon cancer cell targeted delivery of curcumin

Nanogels have potential for encapsulating cancer therapeutics, yet their susceptibility to physiological degradation and lack of cellular specificity hinder their use as effective oral delivery vehicles. Herein, we engineered novel albumin-core with folic acid functionalized hyperbranched amylopectin shell-type nanogels, prepared through a two-step reaction and loaded with curcumin while the proteinaceous core was undergoing thermal gelation. The nanogels had a mean hydrodynamic diameter of ca. 90 nm and ζ-potential of ca. -24 mV. Encapsulation of curcumin within the nanogels was restored, up to ca. 0.05 mg mL-1, beyond which, a gradual increase in size and a decrease in ζ-potential was observed. The core-shell structures were resilient to in vitro physiological oral-gastrointestinal digestion owing to a liquid crystalline B- and V-type polymorphism in the polysaccharide shell, the latter being driven by the shell functionalization with folic acid. Additionally, these biocompatible nanogels restored stability of the encapsulated curcumin and exhibited augmented cellular uptake and retention specifically in folate receptor-positive HT29 human colon adenocarcinoma cells, inducing early-stage apoptosis. Novel insights from this study represent a promising platform for rational designing of future oral delivery systems that can surmount physiological barriers for delivering cancer therapeutics to colon cancer cells with improved stability and specificity

Search for large extra dimensions in the production of jets and missing transverse energy in p(p)over-bar collisions at root s=1.96 TeV

We present the results of a search for new physics in the jets plus missing transverse energy data sample collected from 368 pb(-1) of p (p) over bar collisions at root s = 1.96 TeV recorded by the Collider Detector at Fermilab. We compare the number of events observed in the data with a data-based estimate of the standard model backgrounds contributing to this signature. We observe no significant excess of events, and we interpret this null result in terms of lower limits on the fundamental Planck scale for a large extra dimensions scenario