Mechanisms of Biological Functions Through Polymer Deep Sampling: Protein Gating and Chromatin Folding

We develop probabilistic models of folded biopolymers which allow detailed insight into mechanisms governing many biological processes. Our computational models complement existing experimental techniques which provide valuable measurements but do not provide 3-D structural details that may be key to understanding the underlying biological processes. We demonstrate how the deep probabilistic sampling methodology developed here can be used to discern important properties of both chromatin and protein

Composite 90° and 180° Pulses to Compensate for Radiofrequency Gradients in Toroid NMR Detectors

Two new pulse sequences, a composite 90° pulse and a composite 180° pulse, have been developed to compensate for the extremely large radiofrequency gradients in toroid NMR detectors. The composite 90° pulse has the ability to transfer more than 98% of the equilibrium magnetization phase-correlated into the x-y plane of the rotating frame, even if the strongest B1 held is nine times the weakest. The composite 180° pulse attains 99% inversion of the equilibrium magnetization in the same B1 gradient. Trajectory calculations that follow the fate of the magnetization during the new pulse sequences and during composite pulses reported in the literature compared favorably with results derived from NMR experiments performed within a toroid cavity probe. Also, the T1 relaxation time of chloroform was measured by using the inversion-recovery procedure in a toroid cavity probe. When the standard pulses were substituted by the new composite pulses, the dynamic range in signal intensity was increased by a factor greater than two

Cobalt carbonyl catalyzed olefin hydroformylation in supercritical carbon dioxide

A method of olefin hydroformylation is provided wherein an olefin reacts with a carbonyl catalyst and with reaction gases such as hydrogen and carbon monoxide in the presence of a supercritical reaction solvent, such as carbon dioxide. The invention provides higher yields of n-isomer product without the gas-liquid mixing rate limitation seen in conventional Oxo processes using liquid media

The Toroid Cavity NMR Detector

A cylindrical toroid cavity has been developed as an NMR detector for investigations at high temperature and high pressure in metal vessel probes. With toroid cavity detectors, resonance frequencies up to 400 MHz can easily be attained, which makes them particularly useful for high-field 1H and 19F spectroscopy. Typically, static half-height linewidths of 1.5 Hz are achieved, as measured on 1H with standard solutions in cylindrical pressure vessels. Based on the radial dependency of the B1 field inside a toroid detector, a mathematical equation was derived that precisely predicts the signal intensity as a function of the pulse width. Inversion-recovery measurements of the T1 relaxation time of compressed gases (methane and hydrogen) were conducted by using composite inversion pulses. The results demonstrated the utility of toroid cavities for quantitative measurements in pressure probes. Pressures up to 300 bar have been used successfully. Because of the strength and regularity of the B1 gradient, the toroid cavity detector is also suitable for one dimensional rotating-frame NMR microscopy. A spatial resolution down to a few micrometers can be achieved. The spin concentration and spatial distribution of a chloroform solution were accurately reconstructed from two-dimensional 1H NMR data. Another similarly accurate but even stronger B1 gradient evolves as a result of the skin effect during high-frequency current transmission inside the central conductor. This gradient makes it possible to perform rotating-frame microscopy inside the central conductor, as demonstrated with 63Cu NMR spectroscopy

Video Toroid Cavity Imager

A video toroid cavity imager for in situ measurement of electrochemical properties of an electrolytic material sample includes a cylindrical toroid cavity resonator containing the sample and employs NMR and video imaging for providing high-resolution spectral and visual information of molecular characteristics of the sample on a real-time basis. A large magnetic field is applied to the sample under controlled temperature and pressure conditions to simultaneously provide NMR spectroscopy and video imaging capabilities for investigating electrochemical transformations of materials or the evolution of long-range molecular aggregation during cooling of hydrocarbon melts. The video toroid cavity imager includes a miniature commercial video camera with an adjustable lens, a modified compression coin cell imager with a fiat circular principal detector element, and a sample mounted on a transparent circular glass disk, and provides NMR information as well as a video image of a sample, such as a polymer film, with micrometer resolution

Near-Electrode Imager

An apparatus, near-electrode imager, for employing nuclear magnetic resonance imaging to provide in situ measurements of electrochemical properties of a sample as a function of distance from a working electrode. The near-electrode imager use the radio frequency field gradient within a cylindrical toroid cavity resonator to provide high-resolution nuclear magnetic resonance spectral information on electrolyte materials