Towards the identification of the gold binding region within trypsin stabilized nanoclusters using microwave synthesis routes

Elucidating the location of stabilized nanoclusters within their protein hosts is an existing challenge towards the optimized development of functional protein-nanoclusters. While nanoclusters of various metal compositions can be readily synthesized within a wide array of protein hosts and exhibit tailorable properties, the inability to identify the cluster stabilization region prevents controllable property manipulation of both metallic and protein components. Additionally, the ability to synthesize protein-nanoclusters in a consistent and high-throughput fashion is also highly desirable. In this effort, trypsin stabilized gold nanoclusters are synthesized through standard and microwave-enabled methodologies to determine the impact of processing parameters on the materials physical and functional properties. Density functional theory simulations are employed to localize high probability regions within the trypsin enzyme for Au25 cluster stabilization, which reveal that cluster location is likely within close proximity of the trypsin active region. Trypsin activity measurements support our findings from DFT, as trypsin enzymatic activity is eliminated following cluster growth and stabilization. Moreover, studies on the reactivity of Au NCs and synchrotron characterization measurements further reveal that clusters made by microwave-based techniques exhibit slight structural differences to those made via standard methodologies, indicating that microwave-based syntheses largely maintain the native structural attributes despite the faster synthetic conditions. Overall, this work illustrates the importance of understanding the connections between synthetic conditions, atomic-scale structure, and materials properties that can be potentially used to further tune the properties of metal cluster-protein materials for future applications.

Freestanding organogels by molecular velcro of unsaturated amphiphiles

A simple amphiphile, N-cardanyltaurine amide (NCT) with different degrees of cis-unsaturation in its tail resulted in the formation of strong organogels. Interestingly, this is in contrast to the commonly accepted notion that introducing unsaturation in alkyl chains enhances fluidity in lipid assemblies. The physico-chemical and first-principles DFT calculations confirmed the pegging of 'kinked' unsaturated side chains, where the hydrophobic interlocking as in Velcro fasteners leads to a network of cylindrical micelles, resulting in self-standing organogels. Textural profile analysis and spectroscopic details substantiated the dynamic assembly to resemble a 3D network of gelators rather than being a cross-linked or polymerized matrix of monomers.

Free-energy calculations using classical molecular simulation: application to the determination of the melting point and chemical potential of a flexible RDX model

Several methods are used in sequence to determine the chemical potential of atomistic RDX in the solid and liquid phases, and its corresponding melting point. Results yield the thermodynamic melting point of 488.75 K at 1.0 atm.

Lattice strain due to an atomic vacancy

Volumetric strain can be divided into two parts: strain due to bond distance change and strain due to vacancy sources and sinks. In this paper, efforts are focused on studying the atomic lattice strain due to a vacancy in an FCC metal lattice with molecular dynamics simulation (MDS). The result has been compared with that from a continuum mechanics method. It is shown that using a continuum mechanics approach yields constitutive results similar to the ones obtained based purely on molecular dynamics considerations.

Determination of intraoperative plasma catecholamine concentrations using liquid chromatography with electrochemical detection

Liquid chromatography with electrochemical detection was used for the determination of norepinephrine and epinephrine in human plasma samples obtained prior to, after, and six times during the course of spinal fusion surgery for the correction of scoliosis. The catecholamines were extracted from plasma by alumina adsorption and chromatographed isocratically using a reversed-phase, ion-pairing system. Data obtained are compared to those obtained intraoperatively by other authors using a radioenzymatic method, and the mechanism of sympathetic activation during surgery is discussed. Preliminary data using 3-micron particle size columns and dual-parallel electrochemical detection are presented.

Determination of norepinephrine in brain perfusates using high-performance liquid chromatography with electrochemical detection

A procedure for determining catecholamine levels in brain perfusates is described. A single-step extraction on alumina followed by reversed-phase ion-pair chromatography and electrochemical detection was employed. Levels of norepinephrine are reported in push-pull perfusates of the rat hypothalamus under baseline and various ion substitution conditions. The resulting estimated norepinephrine release values are correlated with the behavior of the animal. The data are discussed in terms of the validity of the measures and the noradrenergic mediation of behavior.

Operant analysis of human heroin self-administration and the effects of naltrexone

The effects of maintenance on a narcotic antagonist, naltrexone (50 mg/day p.o.), or placebo on patterns of operant acquisition and use of heroin were studied under double-blind conditions. Twelve male heroin addict volunteers lived on a clinical research ward for 34 days. After a 9 day drug-free period, naltrexone or placebo were given and heroin) 40 mg/day) was available for 10 days. Subjects could earn money ($1.50) or heroin (10 mg i.v.) by responding on a second-order schedule of reinforcement [FR 300 (FI 1 sec: S)] for approximately 90 min. The three naltrexone-maintained subjects took only 2 to 7.5% of the total heroin available. Two naltrexone subjects stopped heroin self-administration after the 1st or 2nd heroin injection; the third subject took a 3rd heroin injection on the 8th day of heroin availability. Naltrexone maintenance for 25 consecutive days did not produce adverse side effects. In contrast, the nine placebo naltrexone subjects used 57.5 to 100% of the total heroin available. Five placebo subjects used all or all but one of the 40 injections available; four placebo subjects often used less heroin than was available each day. Heroin intoxication did not impair operant performance. Heroin users worked longer hours and earned more purchase points (P < .05) during heroin self-administration and subsequent methadone detoxification than during the drug-free period. Subjects precisely titrated operant work to acquire the desired amount of heroin, then resumed working for money. These data demonstrate the feasibility of using direct measures of drug self-administration behavior to evaluate new pharmacotherapies for heroin abuse and indicate the effectiveness of naltrexone in suppressing heroin self-administration.