Environmental factors, secondary

Like many traits, concentrations of secondary metabolites in algae are determined by a combination of genetic and environmental factors. Secondary metabolites are known to respond to changes in a variety of environmental conditions, including light,14,49,70 herbivory,43" 6, nutrients,44,45,49,73,74 desiccation,75 and salinity.76 Most of these studies have looked at the effects of a single environmental stress at once. However, in nature, multiple stresses often occur simultaneously and may have synergistic effects. 

It is estimated that there are in excess of 20 000 unique chemicals present as plant primary and secondary metabolites (Ohlrogge, 1994). The levels present in foods can vary quite considerably depending on the variety and on agronomic and environmental factors. To attribute benefits to any one chemical or group of chemicals seems a daunting task. Thus, in spite of intensive work in the last decade or so, there is still insufficient evidence with which to support the antioxidant hypothesis , or any other hypothesis, and to attribute... 

Carcinogenic agents include chemicals in the environment, such as aniline and benzene, which are associated with the development of bladder cancer and leukemia, respectively. Environmental factors, such as excessive sun exposure, also may result in cancer. Viruses, including the human papilloma virus and hepatitis B, maybe associated with the development of cancer. Some of the chemotherapy agents cause secondary cancers after therapy has been completed. Numerous factors may contribute to the development of cancer. 

Since the primary structure of a peptide determines the global fold of any protein, the amino acid sequence of a heme protein not only provides the ligands, but also establishes the heme environmental factors such as solvent and ion accessibility and local dielectric. The prevalent secondary structure element found in heme protein architectures is the a-helix however, it should be noted that p-sheet heme proteins are also known, such as the nitrophorin from Rhodnius prolixus (71) and flavocytochrome cellobiose dehydrogenase from Phanerochaete chrys-osporium (72). However, for the purpose of this review, we focus on the structures of cytochromes 6562 (73) and c (74) shown in Fig. 2, which are four-a-helix bundle protein architectures and lend themselves as resource structures for the development of de novo designs. 

Attention deficit hyperactivity disorder (ADHD) For the treatment of ADHD in patients 6 years of age and older. Dexmethylphenidate is indicated as an integral part of a total treatment program for ADHD that may include other measures (eg, psychological, educational, social) for patients with this syndrome. Drug treatment may not be indicated for all patients. Stimulants are not intended for use in the patient who exhibits symptoms secondary to environmental factors or other primary psychiatric disorders, including psychosis. 

Factors that affect rennet coagulation. The effect of various compositional and environmental factors on the primary and secondary phases of rennet coagulation and on the overall coagulation process are summarized in Figure 10.4. 

The three-dimensional structure of a protein does not depend on environmental factors within the cell but is determined solely by the amino add sequence information (Epstein, 1963) this is called the Anfinsen dogma. Model systems of enzymes converted into linear polypeptide chains devoid of disulfide bonds and of secondary and tertiary structures support the theory that the folding process is essentially a thermodynamic one and that no genetic information other than that present in the amino acid sequence of the protein is required. 

Environmental conditions may also affect chemical defense concentrations indirectly by changing the intensity of grazing, which can alter defense concentrations in algae with inducible defenses. Evidence for the direct effects of environmental factors on secondary metabolite concentrations are discussed below. 

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