Tuning Molecular Vibrational Energy Flow within an Aromatic Scaffold via Anharmonic Coupling.

From guiding chemical reactivity in synthesis or protein folding to the design of energy diodes, intramolecular vibrational energy redistribution harnesses the power to influence the underlying fundamental principles of chemistry. To evaluate the ability to steer these processes, the mechanism and time scales of intramolecular vibrational energy redistribution through aromatic molecular scaffolds have been assessed by utilizing two-dimensional infrared (2D IR) spectroscopy. 2D IR cross peaks reveal energy relaxation through an aromatic scaffold from the azido- to the cyano-vibrational reporters in -azidobenzonitrile (PAB) and -(azidomethyl)benzonitrile (PAMB) prior to energy relaxation into the solvent.

Energy Transport across Interfaces in Biomolecular Systems.

Energy transport during chemical reactions or following photoexcitation in systems of biological molecules is mediated by numerous interfaces that separate chemical groups and molecules. Describing and predicting energy transport has been complicated by the inhomogeneous environment through which it occurs, and general rules are still lacking. We discuss recent work on identification of networks for vibrational energy transport in biomolecules and their environment, with focus on the nature of energy transfer across interfaces.

Vibrational States and Nitrile Lifetimes of Cyanophenylalanine Isotopomers in Solution.

Nitrile lifetimes and the structure of the vibrational state space of four isotopomers of cyanophenylalanine in solution are calculated. While the frequency of the nitrile of the four isotopomers decreases in the order CN, CN, CN, and CN, the lifetime varies nonmonotonically with the change in frequency. The vibrational properties of the molecules that control the lifetime are examined.

Small Saccharides as a Blanket around Proteins: A Computational Study.

Saccharides stabilize proteins exposed to thermal fluctuations and stresses. While the effect of a layer of trehalose around a protein on the melting temperature has been well studied, its role as a thermal insulator remains unclear. We report calculations of thermalization in small saccharides, including glucose, galactose, lactose, and trehalose, and thermal transport through a trehalose layer between water and protein and between gold, such as a gold nanoparticle, and its cellular environment.

Thermodynamics of Hydration Water around an Antifreeze Protein: A Molecular Simulation Study.

We investigate by molecular simulations thermodynamic properties of hydration water and protein, the sensitivity of hydrogen bonds to change in temperature, and hydration water distribution at varying levels of hydration of a hyperactive antifreeze protein, DAFP-1. Hydration water coverage of the protein and partial thermodynamic properties of the hydration water are heterogeneous, different for the water near the ice-binding site (IBS) and the rest of the protein, particularly at low levels of hydration. Overall, we find the partial specific heat of water to be larger at low hydration levels than in the fully hydrated limit, with the separation corresponding roughly to one hydration layer.

Influence of thermalization on thermal conduction through molecular junctions: Computational study of PEG oligomers.

Thermalization in molecular junctions and the extent to which it mediates thermal transport through the junction are explored and illustrated with computational modeling of polyethylene glycol (PEG) oligomer junctions. We calculate rates of thermalization in the PEG oligomers from 100 K to 600 K and thermal conduction through PEG oligomer interfaces between gold and other materials, including water, motivated in part by photothermal applications of gold nanoparticles capped by PEG oligomers in aqueous and cellular environments. Variation of thermalization rates over a range of oligomer lengths and temperatures reveals striking effects of thermalization on thermal conduction through the junction.

Thermalization and Thermal Transport in Molecules.

The nature and rate of thermal transport through molecular junctions depend on the length over which thermalization occurs. For junctions formed by alkane chains, in which thermalization occurs only slowly, measurements reveal that thermal resistance is controlled by bonding with the substrates, whereas fluorination can introduce thermal resistance within the molecules themselves, although the mechanism remains unclear. Here we present results of quantum-mechanical calculations of elastic and inelastic scattering rates, the length over which thermalization occurs, and thermal conductance in alkane and perfluoroalkane junctions.

Asymmetric energy flow in liquid alkylbenzenes: A computational study.

Ultrafast IR-Raman experiments on substituted benzenes [B. C. Pein et al.

Comparative study of intrathecal dexmedetomidine with intrathecal magnesium sulfate used as adjuvants to bupivacaine.

Background: No drug, used as adjuvant to spinal bupivacaine, has yet been identified that specifically inhibits nociception without its associated side-effects.

Aims: This prospective randomized double-blind study was conducted to evaluate the onset and duration of sensory and motor block as well as perioperative analgesia and adverse effects of dexmedetomidine and magnesium sulfate given intrathecally with 0.5% hyperbaric bupivacaine for spinal anesthesia.

Comparative study of intravenously administered clonidine and magnesium sulfate on hemodynamic responses during laparoscopic cholecystectomy.

Background: Both magnesium and clonidine are known to inhibit catecholamine and vasopressin release and attenuate hemodynamic response to pneumoperitoneum. This randomized, double blinded, placebo controlled study has been designed to assess which agent attenuates hemodynamic stress response to pneumoperitoneum better.

Materials And Methods: 120 patients undergoing elective laparoscopic cholecystectomy were randomized into 4 groups of 30 each.