The frequency of errors during a single cycle of DNA replication is less than 10-10per base pair. This high accuracy is ascribed to three independent steps of DNA replication; base selection by DNA polymerase, elimination of mismatched nucleotide by proofreading exonuclease and post-replication mismatch repair. In addition, elimination of mutagenic substrate from the precursor pool and repair of damaged DNA template are involved. Defect in any one of genes controlling the above mentioned steps would cause high frequency of spontaneous mutation. Significance of genetic instablility in carcinogenesis is discussed, with special reference to hereditary cancer.
Entropy productions of human, swine, plant leaves and lake-ecosystems are quantitatively discussed based on the results of calculations using observed energetic data. Entropy productions in human body increase rapidly from birth to 16 years of age for male and to 14 years of age for female and then decrease gradually afterwards. Entropy production in plant leaves increases linearly with absorbed solar radiation energy. Entropy production increases in the course of eutrophication in lake-ecosystems.
As the major targets of immunity have been changing from extracellular antigens, such as harmful bacteria and their toxins, to intracellular events caused by viral genes or oncogenes, the main stream of immunology appears to have been shifted from humoral arm to cellular arm. The key effectors of the latter arm are T lymphcytes, in particular CD8+ cytotoxic T lymphocytes (CTL) which can recognize fragmented viral parts or tumor antigens and may control intracellular virus replication or tumor progression. In this review, by modeling human immune deficiency virus (HIV) envelope protein, possible molecular control of cellular immune responses to viral components will be discussed.
Single neuronal activity was recorded in the inferior temporal cortex of rhesus monkeys during a visual discrimination and memory task. A small group of neurons responded to aspecific category of stimuli such as faces or hands. However, many neurons responded to several categories of stimuli. In other words, these neurons were not selective enough to be classified as 'gnostic' neurons. On the other hand, activity of these neurons was dependent on what monkeys recognized rather than what monkeys perceived.
Two-dimensional (2-D) crystallization techniques of proteins are reviewed. The techniques are classified by the differences in the substrates that limit the growth of crystals in two-dimensions. The substrates are required to have strong binding ability to proteins, flatness (on a molecular level), and at times, fluidity. The balance of protein-substrate and protein-protein interactions are critical for 2-D crystallization. Strategies for improving 2-D crystallization are also described.