H NMR Studies of Eukaryotic Cytochrome c

H NMR resonance assignments in the spectra of horse, tuna, Neurmpora crassa and Candida krusei cyto-chromes c are described. Assignments have been made using NMR double-resonance techniques in conjunction with electron-exchange experiments, spectral comparison of related proteins, and consideration of the X-ray structure of tuna cytochrome c. Resonances arising from 11 residues of horse cytochrome c have been assigned

Direct Correlation between Adsorption Energetics and Nuclear Spin Relaxation in a Liquid-saturated Catalyst Material.

The ratio of NMR relaxation time constants T 1 / T 2 provides a non-destructive indication of the relative surface affinities exhibited by adsorbates within liquid-saturated mesoporous catalysts. In the present work we provide supporting evidence for the existence of a quantitative relationship between such measurements and adsorption energetics. As a prototypical example with relevance to green chemical processes we examine and contrast the relaxation characteristics of primary alcohols and cyclohexane within an industrial silica catalyst support. T 1 / T 2 values obtained at intermediate magnetic field strength are in good agreement with DFT adsorption energy calculations performed on single molecules interacting with an idealised silica surface. Our results demonstrate the remarkable ability of this metric to quantify surface affinities within systems of relevance to liquid-phase heterogeneous catalysis, and highlight NMR relaxation as a powerful method for the determination of adsorption phenomena within mesoporous solids.Catalysis@Cambridge, BP pl

Evaluation of the surface affinity of water in three biochars using fast field cycling NMR relaxometry

Many soil functions depend on the interaction of water with soil. The affinity of water for soils can be altered by applying soilamendments like stone meal, manure, or biochar (a carbonaceous material obtained by pyrolysis of biomasses). In fact, the addi-tion of hydrophobic biochar to soil may increase soil repellency, reduce water-adsorbing capacity, inhibit microbial activity, altersoil filter, buffer, storage, and transformation functions. For this reason, it is of paramount importance to monitor water affinity forbiochar surface (also referred to as ‘wettability’) in order to better address its applications in soil systems. In this study, we proposethe use of fast field cycling NMR relaxometry technique with the application of a new mathematical model for data interpretation,as a valid alternative to the traditional contact angle (CA) measurements for biochar wettability evaluation. Either NMR or CA re-sults revealed the same wettability trend for the biochars studied here. The advantage of NMR relaxometry over CA measurementslies in the possibility to obtain at the microscopic level a variety of different information in only one shot. In fact, while CA providesonly wettability evaluation, NMR relaxometry also allows achievement of the mechanisms for water molecular dynamics onbiochar surface, thereby leading to the possibility to understand better, in future research, the role of biochar in increasing soilquality and plant nutrition

Microstructure and texture of hydrated cement-based materials: A proton field cycling relaxometry approach

We show how the measurement of proton nuclear magnetic spin-lattice relaxation as a function of magnetic field strength (and hence nuclear Larmor frequency) can provide reliable information on the microstructure (specific surface area and pore size distribution) throughout the progressive hydration of cement-based materials. We present in details the experimental and theoretical characteristic features of the relaxation dispersion to support an interpretation in terms of coupled solid-liquid relaxation at pore interfaces, surface diffusion, and nuclear paramagnetic relaxation. The measurement does not require any drying temperature modification and is sufficiently fast to be applied continuously during the progressive hydration of the material. Coupling this method with the standard proton nuclear spin relaxation and high resolution NMR allows us to follow the development of micro-scale texture within the material. (C) 2006 Elsevier Ltd. All rights reserved