Effect of moisture and oxygen

Pikal, M. J., Dellermann, K., Roy, M. L Formulation and stability of freeze-dried proteins Effects of moisture and oxygen on the freeze-dried formulation of human growth hormones. Developments in Biological Standardization, Vol. 74, p. 21-38. Acting Editors Joan C. May - F. Brown. S. Karger AG, CH-4009 Basel (Switzerland), 1992... 

Effects of Moisture and Oxygen in the Fate of PPCPs in the Environment... 

M. J. Pikal, K. Dellerman and M. L. Roy, Formulation and stability of freeze-dried proteins effects of moisture and oxygen on the stability of freeze-dried formulations of human growth hormone. Dev. Biol. Stand. 74. 21-38 (1991). 

Pikal et al. [33] also looked at effects of moisture and oxygen on the formulation and stability of freeze-dried human growth hormone evaluating the formation of irreversible aggregates. 

The effect of plasticizers and temperature on the permeabiUty of small molecules in a typical vinyUdene chloride copolymer has been studied thoroughly. The oxygen permeabiUty doubles with the addition of about 1.7 parts per hundred resin (phr) of common plasticizers, or a temperature increase of 8°C (91). The effects of temperature and plasticizer on the permeabiUty are shown in Figure 4. The moisture (water) vapor transmission rate (MVTR or WVTR) doubles with the addition of about 3.5 phr of common plasticizers (92). The dependence of the WVTR on temperature is a Htde more comphcated. WVTR is commonly reported at a constant difference in relative humidity and not at a constant partial pressure difference. WVTR is a mixed term that increases with increasing temperature because both the fundamental permeabiUty and the fundamental partial pressure at constant relative humidity increase. Carbon dioxide permeabiUty doubles with the addition of about 1.8 phr of common plasticizers, or a temperature increase of 7°C (93). 

Artificial skin had been made from a bilayer fabricated from a cross-linked mixture of bovine hide, collagen, and chondroitin-B-sulfate derived from shark cartilage with a thin top layer of siloxane. The siloxane layer acts as a moisture- and oxygen-permeable support and to protect the lower layer from the outer world allowing skin formation to occur in conjunction with the lower layer. Poly(amino acid) films have also been used as an artificial skin. Research continues in search of a skin that can be effectively used to cover extensive wounds and for burn patients. 

In these polymer-metal complexes of the Werner type, however, organometallic compounds are formed as reaction intermediates and/or activated complexes. As a result, the properties of polymer-metal catalysts in reductive reactions are different from those of polymer-metal catalysts in oxidative reactions. In the former, the catalytic reactions are very sensitive to moisture and air, and the complex catalysts often decompose in the presence of water and oxygen. Thus, reductive catalytic reactions are carried out under artificial conditions such as organic solvent, high pressure, and high temperature. Oxidative catalytic reactions, on the other hand, proceed under mild conditions aqueous solution, oxygen atmosphere, and room temperature. Therefore, it is to be expected that the catalytic effects of a polymer ligand will differ from the latter to the former. 

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