Hydrogenation of biological systems

There is a general understanding of the reasons why nutrients are critical to the productive capacity of biological systems. The dry biomass of plants and animals comprises some 20 elements, the predominant atoms being those of carbon, hydrogen, oxygen, and nitrogen. Moreover, ideally they are required in fairly... 

HA can be produced by catalytic oxidation of ammonia with hydrogen peroxide or by catalytic reduction of nitrates with hydrogen . Analogously, oxidative and reductive enzymic pathways in which HA is produced from either ammonia or nitrate have been identified in a variety of biological systems. 

Hydrogen bonding of the type N-H N formed between molecules of imidazole and its derivatives is closely related to a variety of biological systems and has been a subject of extensive studies using a variety of spectroscopic and diffraction techniques. In crystalline imidazole, the molecules form a one-dimensional chain of intermolecular N-H N hydrogen bonding, a schematic representation of which is shown below. 

Water behaves differently in different environments. Properties of water in heterogenous systems such as living cells or food remain a field of debate. Water molecules may interact with macromolecular components and supramolecular structures of biological systems through hydrogen bonds and electrostatic interactions. Solvation of biomolecules such as lipids, proteins, nucleic acids, or saccharides resulting from these interactions determines their molecular structure and function. 

In the following sections, some recent work in this field is reviewed. In a number of cases, references are given to recent publications with discussions of earlier work. The main focus is on IR investigations of key phenols that serve as reference compounds, particularly in relation to the study of hydrogen bonding effects. IR spectroscopy of biological systems is considered to fall outside the scope of this survey. For an example... 

Liquid water molecules have a limited capacity to ionize to form H+ and OLL ions. The concentration of hydrogen ions is a crucial feature of biological systems primarily because of their effects on biochemical reaction rates and protein structure. Buffers, which consist of weak acids and their conjugate bases, prevent changes in pH (a measure of [H+]). 

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