Isotypes

The basic structure of all immunoglobulin (Ig) molecules comprises two identical light chains and two identical heavy chains linked together by disulfide bonds (Figure IS.2a). There are two different classes, or isotypes, of light chains, X and k, but there is no known functional distinction between them. Heavy chains, by contrast, have five different isotypes that divide the immunoglobulins into different functional classes IgG, IgM, IgA, IgD, and IgE, each with different effector properties in the elimination of antigen... 

In addition to the heteronuclear clusters considered in the preceding paragraphs. As, Sb and Bi also form homonuclear clusters. We have already seen that alkaline earth phosphides M3P14 contain the [Pv] cluster isoelectronic and isostructural with P4S3, and the analogous clusters [Asy] " and [Sbv] have also been synthesized. Thus, when As was heated with metallic Ba at 800° C, black lustrous prisms of BasAs were obtained, isotypic with Ba3Pi4 these contained the [Asv] anion with dimensions as shown in Fig. 13.25(a).Again,... 

The other tetrahalides can all readily be made by direct reactions of the elements. Crystalline SeCU, TeCU and -SeBr4 are isotypic and the structural unit is a cubane-like tetramer of the same general type as [Me3Pt(/Z3-Cl)]4 (p. 1168). This is illustrated schematically for TeCU in Fig. 16.13d each Te is displaced outwards along a threefold axis and thus has a distorted octahedral environment. This can be visualized as resulting from repulsions due to the Te lone-pairs directed towards the cube centre and, in the limit, would result in the separation into... 

Reprinted from Journal of High Resolution Chromatography, 15, S. Nitz et ah, Multidimensional gas chi omatography-isotype ratio mass spectrometry (MDGC-IRMS). Part A system description and technical requirements, pp. 387-391, 1992, with peraiission from Wiley-VCH. 

Prasher, D. C., McCann, R. O., Longiaru, M., and Cormier, M. J. (1987). Sequence comparisons of complememtary DNAs encoding aequorin isotypes. Biochemistry 26 1326-1332. 

Ranganathan S, Benetatos CA, Colamsso PJ et al (1998) Altered beta-tubulin isotype expression in paclitaxel-resistant human prostate carcinoma cells. Br J Cancer 77 562-566... 

Two isotypes of SUR have been cloned, SUR1 and SUR2. In addition, two splicing variants of SUR2, distinguished by 42 C-terminal amino acids, have been... 

For some of the GLUT isotypes, the phenotype of null mutants is known. Haploinsufficiency of the GLUT1 in... 

Insulin Analogs. At present, the only known ligands of the insulin receptors are insulin isotypes from different species and a number of synthetic analogs... 

The tissue-specific patterns of expression of the PPAR. isotypes suggested that these proteins have distinct physiological roles, and this was further supported when each was specifically disrupted in mouse gene knockout models. 

The expression of all three PPAR isotypes peaks in the rat central nervous system between days 13.5-18.5 of gestation, and while expression of both PPARa and PPARy decline post-natally, expression of PPARS remains high (except for the retina, where all three isoforms are expressed in the adult rodent). An important role for PPARS in CNS development is underscored by the occurrence of defective myelination in the PPARS-null mouse. 

Epidermal Maturation and Wound Healing. All three PPAR isotypes are expressed during epidermal maturation each isotype has a specific pattern of expression in regard to development and the various layers of the epidermis. An important role for PPARS in the development and/or maintenance of normal skin health is indicated by the presence of defective wound healing in the PPARS-null mouse. 

Table 4 summarizes the physiological functions of the PPAR isotypes and their synthetic ligands. 

PPAR isotype Tissues of highest expression Primary physiological effects Endogenous ligands Synthetic ligands Associated disease state/ indication... 

It is an autoantibody whose autoantigen is the Fc portion of IgG. Rheumatoid factors may be of any immunoglobulin isotype but it is IgM rheumatoid factor that is commonly measured in rheumatoid arthritis. Classification criteria for rheumatoid arthritis include only one serological test, namely rheumatoid factor. However, it is not diagnostic test rather it may be confirmatory when a number of other clinical features are present. 

Cytokine receptors that couple to the JAK-STAT Pathway decode the signaling though hematopoietic cytokines (erythropoietin, thrombopoietin, colony-stimulating factors), prolactin, growth hormone, the a-, (3- and y- interferons, and a number of immunomodulatory interleukins [3], They form homodimetic or heterodimeric receptor complexes, which after ligandbinding recruit and activate isotypes of Janus kinases (JAKs). Activated JAKs in turn... 

Isomorphism. Like TiC, ZrC forms solid solutions with oxygen and nitrogen, which have a wide range of composition. The lattices of ZrC, ZrN, and ZrO are isotypical. ZrC forms solid solutions with the other monocarbides of Group IV and V. 

Sullivan, K.F. (1988). Structure and utilization of tubulin isotypes. Ann. Rev. Cell Biol. 4,687-716. 

For crystallographic data, see Table I. The compounds of the type CuTeX and CuTe X (X = Cl, Br, or I), respectively, are isotypic, and their crystal structures have been determined. Copper has the oxida-... 

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