摘要:

AbstractModel studies of molecular recognition are reviewed with emphasis on contributions from macrocyclic chemistry. Recent developments concerning new molecular shapes are discussed. The advantages of a molecular cleft are presented. In these structures functional groups converge to create a microenvironment complementary to substrates. Specifically, di‐, tri‐ and tetracarboxylic acids of varying sizes are shown to recognize smaller molecules of complementary shape. The new receptors function by a combination of hydrogen bonding and aryl stacking interactions. Substrates include amines, acids, amino acids, metal ions and nucleotide components. The relationship between functional group orientation and catalysis is explored and two systems capable of concerted acid/base catalysis are introdu

ISSN:0952-3499    

DOI:10.1002/jmr.300010103

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractBy employing the principles of “activated swelling”, monosized, superparamagnetic polymer particles have been prepared ranging in size from 1–100 μm. Both during and after the swelling process, the particles can be modified to meet a series of specific demands making them potentially very interesting for many separation and assay purposes.Using monoclonal antibodies to direct the magnetic beads to their targets, immunomagnetic separation has turned out to be one of the most specific, reliable and, above all, the fastest technique available today to isolate particulate material for further studies. So far, most efforts have been concentrated on methodology for fractionation of cells in suspension, such as removal of tumour cells from bone marrow or isolation of lymphoid cells from peripheral blood. These studies have both established the parameters necessary for optimal performance and at the same time laid the groundwork for future developments making immunomagnetic separation an exciting new tool in many research areas.High speed and specificity are the most conspicuous features of immunomagnetic cell separation. These properties have been exploited in the successful development of a new technique for tissue typing of cells directly from peripheral blood specimens. Both higher sensitivity and specificity have been obtained. The same principles can be used for fast and safe quantification of cell populations and subpopulations in blood and cell suspensions.The functions of, and interactions between, peripheral blood cell populations or subpopulations in the immune response have also been studied with high precision. The significance of direct cell contact on the one hand, and soluble factors on the other, can now be established in detail. Immunomagnetic beads have also been used to study the interaction between various T lymphocyte membrane molecules in the early phases of the activation process.Finally, the usefulness of specially developed particles for the fractionation of subcellular components is des

ISSN:0952-3499    

DOI:10.1002/jmr.300010104

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractWe have investigated a possible molecular basis for mitochondrial cristae formation. Proteoliposomes containing electron transport proteins, cytochrome oxidase, or complex III in their proper orientation bind to pig heart mitoplasts but not pig heart mitochondria. Using Leydig tumor cells, we have confirmed earlier reports that chloramphenicol causes a diminution in cristae content and a change in its characteristic lamellar form. We show that the proteoliposomes containing cytochrome oxidase or complex III in the proper orientation bind to mitoplasts from Leydig tumor cells but do not bind as well to mitoplasts from chloramphenicol‐treated Leydig tumor cells. These experiments provide a possible mechanism to explain cristae formatio

ISSN:0952-3499    

DOI:10.1002/jmr.300010105

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe Insulin receptor is an integral transmembrane glycoprotein comprised of two α‐(∼ 135kDa) and two β‐(∼ 95kDa) subunits, which is synthesized as a single polypeptide chain precursor (αβ). The primary sequence of the human insulin receptor (hIR) protein, deduced from the nucleotide sequence of cloned human placental mRNAs, predicts two large domains (929 and 403 residues) on either side of a single membrane spanning domain (23 residues); each of these major domains has a distinct function (insulin binding and protein/tyrosine kinase activity, respectively). To experimentally test this deduced topology, and to explore the potential for independent domain function by the hIR extracellular domain, we have constructed an expression plasmid encoding an hIR deletion mutant which is truncated 8 residues from the beginning of the predicted transmembrane domain (i.e., 921 residues). This domain of the hIR is in fact processed into α‐and truncated β‐subunits and secreted with high efficiency from transfected CHO cell lines which express this mutant hIR, and the protein accumulates as an (αβ)2dimer in the medium. This molecule is recognized by a battery of 13 monoclonal antibodies to epitopes on the IR extracellular domain, four of which block insulin binding and two of which require the native conformation of the IR for recognition. Further, this domain, binds insulin with an apparent dissociation constant comparable to that of the wild‐type hIR. However, the secreted dimmer displays a linear Scatchard plot, while that of the wild‐type membrane‐associated hIR curvilinear. These results, together with previous results with a soluble derivative of the hIR cytoplasmic protein/tyrosine kinase domain, are consistent with the deduced topology. The IR is indeed comprised of two large soluble domains connected by a single membrane spanning domain, which on the one hand act concert upon ligand binding (insulin‐dependent activation of the protein/tyrosine kinase) to initiate the insulin response in cells, but on the other hand are each capable of autonomous function (ligand binding and protein/tyrosine kin

ISSN:0952-3499    

DOI:10.1002/jmr.300010106

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractWe sought to identify the features controlling the specificity of antibody recognition and thus gain insights into molecular recognition between proteins in general. A total of 103 epitopes with in 63 well‐defined antigenic peptides homologous with the relevant antigen sequence were identified. The contribution of each amino acid residue to the antibody binding activity of each apitope was investigated by ELISA testing of complete sets of peptide analogs containing single amino acid replacements. The data are summarized in a replaceability matrix. Some of the high frequency replaceabilities were expected, such as aspartate for glutamate, serine for threonine, etc., but unexpected relationships were also found, such as a high degree of acceptability of methionine as a replacement. Replaceability with a residue of opposite charge was rare. Glycine and tyrosine were frequently of low acceptability, except for glycine as a replacement for alanine. It was found that on average only about four to five amino acid residues in epitopes were required to determine specificity and provide binding energy. Specificity and binding energy were attributed to amino acid side chains rather than main chain atoms. Propensity factors for occurrence of amino acids in antigenic determinants were calculated. The prominence of certain hydrophobic residues as residues critical to recognition by antibody suggests that the molecular surface of an antigen in its combined from with antibody is altered from that occurring in the absence of antibody. Thus, antigenicity is not a static surface phenomenon but depends on the ability of the antigen to undergo rearrangement, supporting the induced fit concep

ISSN:0952-3499    

DOI:10.1002/jmr.300010107

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractA semi‐synthetic protein design approach has been employed for the structural investigation of a putative helical region at the C‐terminus of Interleukin‐2. With crystallographic or NMR derived conformational data as yet unavailable, we have relied only on primary sequence information and computer‐assisted modelling to direct the analysis. By employing both chemical peptide synthesis and recombinant DNA methods, the C‐terminus of IL‐2 was modified according to a strategy designed to stabilize helical secondary structure. A semi‐synthetic protein incorporating 12 simultaneous amino acid replacements was constructed, which possessed potentiated biological activity and displayed a far UV circular dichroism spectrum comparable to a hybrid protein with the authentic sequence. By comparison, another hybrid protein containing a C‐terminal region designed to contain helix breaking residues was totally devoid of bioactivity. These findings provide evidence that the modelling method correctly identified a helix necessary for the formation of a bioactive tertiary fold. Moreover, by employing semi‐synthesis it was possible to circumvent the difficulties associated with the preparation, purification and analysis of multiple recombinant proteins, and also to avoid the unreliability of total chemical synthesis for proteins greater

ISSN:0952-3499    

DOI:10.1002/jmr.300010108

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractWe have isolated a highly enriched preparation of the multienzyme complex which synthesize Deocyribonuleoside triphosphates (dNTPs) from bacteriophage T4‐infected bacteria. By a combination of SDS polyacrylamide gel electrophoresis and assays for specific enzyme activities, we have been able to identify in our final preparation ten different gene products which were previously identified as constituents of this complex, based upon studies with crude preparation. The complex dissociates at high concentrations of NaCl and MgCl2but is stable under ionic conditions thought to exitsin vivo. The purified complex catalyzes the efficient five‐step conversion of dCTP to dTTP. Experiments with several T4 mutants have demonstrated that gene product encoded bycd,regA,nrdA, andnrdB are necessary to retain physical integrity of the complex throughout the preparative procedure, while gp44, gp55, and gppseT are not required. We conclude from this evidence that the T4 early gene products which function in dNTP biosynthesis are, in fact, physically linked as a multienzyme complex, and thatregA contributes to the integrity of this complex. However, the dNTP‐synthesizing complex as we isolate it contains no detectable DNA polymerase, nor have other known replication proteins been det

ISSN:0952-3499    

DOI:10.1002/jmr.300010109

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

ISSN:0952-3499    

DOI:10.1002/jmr.300010110

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

ISSN:0952-3499    

DOI:10.1002/jmr.300010102

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY