Hydrogen-deuterium exchange experimental techniques

Recent experimental developments in coupling IR spectroscopy techniques with mass spectrometry, which allow the structural characterization of isolated and microsolvated protonated aromatic molecules in the gas phase have been summarized.64 Hydrogen-deuterium exchange has been observed at Ha in (59) and some closely related substrates when this ligand is complexed to Cu1 in [2Hg]acetone.65 The process is finely controlled by the precise coordination distance required to form agostic interaction between Cu(I) and the C-H bond and is believed to involve the enol form of [2H6]acetone and a reversible Cu(I) to Cu(III) interconversion. 

An alternative technique for the separation of the crystalline and amorphous contributions to the absorption bands of functional groups containing labile hydrogen atoms (e.g. —OH, —NH) is deuterium exchange (see below). The principal advantage of this experimental method is that it offers the possibility of studying independently the preferential alignment of chemically identical structural units in different phases of the polymer. 

Several experimental techniques have have been used to study conformational flexibility in protein molecules. Spectroscopic methods such as NMR, ESR, Mossbauer, and fluorescence techniques provide direct and detailed studies of internal motions in proteins. Hydrogen-deuterium (or tritium) exchange methods are particularly convenient for kinetic studies. Immuno-chemistry may be also a very helpful method to study conformational fluctuations. These results are discussed in the second part of this volume. 

A tracer technique was employed in an effort to gain further information about the reaction mechanism (10). One alpha hydrogen atom of n-octyl alcohol was replaced with an atom of deuterium. The steps of the two reaction mechanisms under discussion are presented in Fig. 2. If the exchange between hydrogen and deuterium is small, the presence of significant quantities of deuterium in the gaseous product may be explained only by mechanism (1). The exact experimental details of this investigation will now be discussed. 

In this section, the theoretical basis of SANS will be exposed as is needed in polymer physics and will be clarified with simple experimental examples. Since the end of 1939, the method of SAS was developed by Guinier and Kratky and was mainly applied for questions in metal physics. In one of his first experiments, Guinier correctly interpreted scattering from copper precipitates in aluminum, the so-called Guinier-Preston zones. Today, SANS techniques are broadly used in soft matter a main reason is the relatively simple possibilities of contrast generation and variation for polymer chains and other hydrocarbon molecular items by the exchange of hydrogen and deuterium. 

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