InSitμ@CHESS,a Resource for Studying Structural Materials

High-energy X-ray diffraction (HEXD) experiments, which include real-time measurements of micromechanical material response using in-situ loading and the non-destructive creation of three-dimensional maps of polycrystalline microstructure, are very rapidly replacing traditional macroscopic mechanical tests and forensic metallurgical characterization methods for structural materials. The center for Integrated Simulation and X-ray Interrogation Tools and Training for Micromechanics at the Cornell High Energy Synchrotron Source (InSitμ@CHESS) was created to facilitate the use of HEXD experiments on structural materials; more notably, metallic alloys such as steel, titanium, aluminum, and nickel. The Office of Naval Research (ONR) has financially supported InSitμ, specifically enabling enhanced industrial user support. This article describes the experimental considerations associated with using HEXD on structural materials and, through a set of examples, illustrates how InSitμ addresses these considerations.     

Biopreservation of Chocolate Mousse with Lactobacillus helveticus 2/20: Microbial Challenge Test

Probiotic bacteria are used for food biopreservation because their metabolic products might contribute to ensuring food microbiological safety and/or increase its shelf life without the addition of chemical preservatives. Moreover, biopreserved foods are excellent vehicles for the delivery of probiotic bacteria. The aim of the study was to investigate the potential of chocolate mousse food matrix for the delivery of the probiotic strain Lactobacillus helveticus 2/20 (Lb. helveticus 2/20) and to investigate its capacity to inhibit the growth of two foodborne pathogenic bacteria (Staphylococcus aureus and Escherichia coli). Therefore, the populations of free or encapsulated in calcium alginate Lb. helveticus 2/20 cells and/or of each pathogen (used to voluntarily contaminate each sample) were monitored both in complex nutrient medium (MRS broth) and in chocolate mousse under refrigeration conditions and at room temperature. Lb. helveticus 2/20 alone in free or encapsulated state effectively inhibited the growth of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 in chocolate mousse when stored at 20 ± 2 °C. Practically no viable unwanted bacteria were identified on the 7th day from the beginning of the process. High viable Lb. helveticus 2/20 cell populations were maintained during storage under refrigerated conditions (4 ± 2 °C) and at room temperature. Chocolate mousse is thus a promising food matrix to deliver probiotic Lb. helveticus 2/20 cells, which could also protect it from contamination by unwanted bacteria.     

Role of solvent for globular proteins in solution

The properties of the solvent affect the behavior of the solution. We propose a model that accounts for the contribution of the solvent free energy to the free energy of globular proteins in solution. For the case of an attractive square-well potential, we obtain an exact mapping of the phase diagram of this model without solvent to the model that includes the solute-solvent contribution. In particular we find for appropriate choices of parameters upper critical points, lower critical points, and even closed loops with both upper and lower critical points similar to those found before [Macromolecules 36, 5843 (2003)]. In the general case of systems whose interactions are not attractive square wells, this mapping procedure can be a first approximation to understand the phase diagram in the presence of solvent. We also present simulation results for both the square-well model and a modified Lennard-Jones model.     

A finite-size scaling study of a model of globular proteins

Grand canonical Monte Carlo simulations are used to explore the metastable fluid-fluid coexistence curve of the modified Lennard-Jones model of globular proteins of ten Wolde and Frenkel [Science, 277, 1975 (1997)]. Using both mixed-field finite-size scaling and histogram-reweighting methods, the joint distribution of density and energy fluctuations is analyzed at coexistence to accurately determine the critical-point parameters. The subcritical coexistence region is explored using the recently developed hyper parallel tempering Monte Carlo simulation method along with histogram reweighting to obtain the density distributions. The phase diagram for the metastable fluid-fluid coexistence curve is calculated in close proximity to the critical point, a region previously unattained by simulations.     

Simple model of membrane proteins including solvent

We report a numerical simulation for the phase diagram of a simple two-dimensional model, similar to the one proposed by Noro and Frenkel [J. Chem. Phys. 114, 2477 (2001)] for membrane proteins, but one that includes the role of the solvent. We first use Gibbs ensemble Monte Carlo simulations to determine the phase behavior of particles interacting via a square-well potential in two dimensions for various values of the interaction range. A phenomenological model for the solute-solvent interactions is then studied to understand how the fluid-fluid coexistence curve is modified by solute-solvent interactions. It is shown that such a model can yield systems with liquid-liquid phase separation curves that have both upper and lower critical points, as well as closed loop phase diagrams, as is the case with the corresponding three-dimensional model.     

Suppression of nitric oxide production in mouse macrophages by soybean flavonoids accumulated in response to nitroprusside and fungal elicitation

Background

The anti-inflammatory properties of some flavonoids have been attributed to their ability to inhibit the production of NO by activated macrophages. Soybean cotyledons accumulate certain flavonoids following elicitation with an extract of the fungal pathogen Diaporthe phaseolorum f. sp. meridionalis (Dpm). Sodium nitroprusside (SNP), a nitric oxide donor, can substitute for Dpm in inducing flavonoid production. In this study, we investigated the effect of flavonoid-containing diffusates obtained from Dpm- and SNP-elicited soybean cotyledons on NO production by lipopolysaccharide (LPS)- and LPS plus interferon-γ (IFNγ)-activated murine macrophages.

Results

Significant inhibition of NO production, measured as nitrite formation, was observed when macrophages were activated in the presence of soybean diffusates from Dpm- or SNP-elicited cotyledons. This inhibition was dependent on the duration of exposure to the elicitor. Daidzein, genistein, luteolin and apigenin, the main flavonoids present in diffusates of elicited cotyledons, suppressed the NO production by LPS + IFNγ activated macrophages in a concentration-dependent manner, with IC₅₀ values of 81.4 μM, 34.5 μM, 38.6 μM and 10.4 μM respectively. For macrophages activated with LPS alone, the IC₅₀ values were 40.0 μM, 16.6 μM, 10.4 μM and 2.8 μM, respectively. Western blot analysis showed that iNOS expression was not affected by daidzein, was reduced by genistein, and was abolished by apigenin, luteolin and Dpm- and SNP-soybean diffusates at concentrations that significantly inhibited NO production by activated macrophages.

Conclusions

These results suggest that the suppressive effect of flavonoids on iNOS expression could account for the potent inhibitory effect of Dpm- and SNP-diffusates on NO production by activated macrophages. Since the physiological concentration of flavonoids in plants is normally low, the treatment of soybean tissues with SNP may provide a simple method for substantially increasing the concentration of metabolites that are beneficial for the treatment of chronic inflammatory diseases associated with NO production.

     

Hyaluronic Acid (HA)‐Based Silk Fibroin/Zinc Oxide Core–Shell Electrospun Dressing for Burn Wound Management

Burn injuries represent a major life‐threatening event that impacts the quality of life of patients, and places enormous demands on the global healthcare systems. This study introduces the fabrication and characterization of a novel wound dressing made of core–shell hyaluronic acid–silk fibroin/zinc oxide (ZO) nanofibers for treatment of burn injuries. The core–shell configuration enables loading ZO—an antibacterial agent—in the core of nanofibers, which in return improves the sustained release of the drug and maintains its bioactivity. Successful formation of core–shell nanofibers and loading of zinc oxide are confirmed by transmission electron microscopy, Fourier‐transform infrared spectroscopy, and energy dispersive X‐ray. The antibacterial activity of the dressings are examined against Escherichia coli and Staphylococcus aureus and it is shown that addition of ZO improves the antibacterial property of the dressing in a dose‐dependent fashion. However, in vitro cytotoxicity studies show that high concentration of ZO (>3 wt%) is toxic to the cells. In vivo studies indicate that the wound dressings loaded with ZO (3 wt%) substantially improves the wound healing procedure and significantly reduces the inflammatory response at the wound site. Overall, the dressing introduced herein holds great promise for the management of burn injuries.     

Phase behavior of short-range square-well model

Various Monte Carlo techniques are used to determine the complete phase diagrams of the square-well model for the attractive ranges lambda = 1.15 and lambda = 1.25. The results for the latter case are in agreement with earlier Monte Carlo simulations for the fluid-fluid coexistence curve and yield new results for the liquidus-solidus lines. Our results for lambda = 1.15 are new. We find that the fluid-fluid critical point is metastable for both cases, with the case lambda = 1.25 being just below the threshold value for metastability. We compare our results with prior studies and with experimental results for the gamma(II)-crystallin.     

Lifetimes and transition probabilities in Kr V

Weighted oscillator strengths (gf), weighted transition probabilities (gA) and lifetimes are presented for all experimentally known dipole transitions and levels of Kr V. Values were determined by four methods. Three of them are based on the Hartree–Fock method, including relativistic corrections and core-polarization effects, with electrostatic parameters optimized by a least-squares procedure in order to obtain energy levels adjusted to the corresponding experimental values. The fourth method is based on a relativistic multiconfigurational Dirac–Fock approach. In addition, 47 new classified lines belonging to the Kr V spectrum are presented.