Stabilization of Free Radicals at Low Temperatures

Active Nitrogen.

“…The decrease in intensity was accompanied by a temperature rise. Addition of NO removed N via NO + N -» N2 + O At the extinction point of the above reaction, all N are converted to O; addition of N2O at this point caused an even greater heat release, indicating that reaction (25) actually produces more heat-releasing species.…”

MacroMolecular Complexes

“…The use of liquid helium as an indispensable refrigerant for attaining temperatures close to absolute zero is based on important recent developments in the fields of low-temperature chemistry ( Klein and Scheer, 1958) and free-radical research (Broida, 1957;Minkoff, 1959). The temperature domain below the glassy transformation of H. Fernandez-Moran.…”

Macromolecular Complexes

“…That coohng to temperatures close to absolute zero does not appreciably impair critical life processes has now been amply demonstrated by the survival of a wide variety of living organisms, including bacteria, spermatozoa, and many other sensitive cells and tissues, which are first treated protectively with glycerol, then frozen with liquid nitrogen or liquid helium, and subsequently thawed in a controlled manner (Harris, 1954;' Lovelock, 1953;Parkes, 1951 ) . By ultrarapid cooling to low enough temperatures, it may be feasible to preserve the original position and relationship of the main organic and inorganic con-stituents of cellular organization in tissues, including the predominant water component, the transient intermediates with unpaired electron-spin (which participate in enzymatic reactions and metabolic electron transfer), and other unstable chemical species generally referred to as free radicals (Broida, 1957;Minkoff, 1959).…”

“…The use of liquid helium as an indispensable refrigerant for attaining temperatures close to absolute zero is based on important recent developments in the fields of low-temperature chemistry ( Klein and Scheer, 1958) and free-radical research (Broida, 1957;Minkoff, 1959 water at -130°C, which had been set aside bv the biologist as a "sanctuary" protecting all life processes from further change, corresponds in fact to the upper limit of the vigorous new field of lowtemperature chemistry. This discipline concerns itself mainly with the wide variety of low-temperature reactions which occur below 150°K and are characterized by low activation energies of 5 kcal/ mol or less.…”

“…Recently, these authors have shown that even at 20°K h\'drogen atoms will react with solid oxvgen. Free radicals and many other unstable chemical species will exhibit considerable reactivity at 70°K (Broida, 1957), and the trapping of these transient intermediates by freezing into an inert solid at liquid helium temperatures (Minkoff, 1959) has been the subject of considerable investigation. Free radicals and other intermediates with unpaired electron-spin play an important role in many enzymatic reactions and in photosynthetic processes .…”