Monomeric Types Research Articles

Kinetic model of two-monomer polymerization.

We propose a kinetic gelation model of polymer growth with two monomeric types that have distinct functionalities (reaction sites), and can polymerize using different reaction types. The heterotypic aggregation of two monomer types is modeled using a moment generating function approach by tracking the temporal evolution of a closed system of moment equations up until gelation. We investigate several scenarios of polymerization with two distinct monomers that differ in the types of reactions that can occur. We determine numerical and analytical conditions for finite time blow-up (the emergence of an oligomer of infinite size) that depend on initial conditions, reaction rates, and number of reaction sites per monomer.

Hoechst 33258—poly(dG-dC)·poly(dG-dC) Complexes Of Three Types

It was found recently that Hoechst 33258, a dsDNA fluorescent dye used in cytological studies, is an efficient inhibitor of the interaction of TATA-box-binding protein with DNA, DNA topoisomerase I, and DNA helicases. In addition it proved to be a radioprotector. Biological activity of Hoechst 33258 may be associated with dsDNA complexes of not only monomeric, but also dimeric type. In this work, the Hoechst 33258 interaction with poly(dG-dC)·poly(dG- dC) was studied using UV-vis and fluorescent spectroscopy, circular and flow-type linear dichroism. It was found that Hoechst 33258 formed with poly(dG-dC)·poly(dG-dC) complexes of three types, namely, monomeric, dimeric, and, apparently, tetrameric, and their spectral properties were studied. Complexes of monomeric and dimeric types competed with distamycin A, a minor groove ligand, for binding to poly(dG-dC)·poly(dG-dC). We proposed that Hoechst 33258 both monomers and dimers form complexes of the external type with poly(dG-dC)·poly(dG-dC) from the side of the minor groove.

Orangutan alpha-satellite monomers are closely related to the human consensus sequence.

Alpha-satellite is a family of tandemly repeated DNA found at the centromeric regions of all human and primate chromosomes. Human alpha-satellite subsets are largely chromosome-specific and have been further grouped into four suprachromosomal families (SFs), each characterized by a unique set of monomeric types. Although chimpanzee and gorilla alpha-satellites share sufficient sequence similarity to fit the established SFs, the assumption that the derived human alpha-satellite consensus and monomeric types represent the sequence of ancestral repeats remains unestablished. By using oligonucleotide primers specific for a conserved region of human alpha-satellite DNA, we have PCR amplified, cloned, and characterized alpha-satellite sequences from the orangutan genome. Nucleotide sequence analysis demonstrated that orangutan alpha-satellite is formed by a single monomeric type that is significantly closer in percentage of sequence identity (mean = 92%, range = 89-96%) to the overall consensus of human alpha-satellite than to the monomeric types corresponding to the four SFs. Use of cloned sequences as hybridization probes to orangutan genomic DNA digested with a panel of restriction enzymes showed that most orangutan alpha-satellite subsets are characterized by a monomeric construction. The subset homologous to clone PPY2-5 is organized in distinct higher-order repeat structures consisting of 18 adjacent monomers. By FISH two clones, PPY3-4 and PPY3-5, proved to be specific for the alpha-satellite on the orangutan homologs of human Chromosomes (Chrs) 10 and 8, respectively. Our data indicate that there was an ancestral monomeric type displaying high sequence similarity to the overall human consensus from which the different great ape and human subsets and SFs may have originated.

β 1 integrins and osteoclast function: Involvement in collagen recognition and bone resorption

The extracellular matrix of bone is composed mainly of type I collagen. In this report we studied the role and collagen binding properties of osteoclast integrins ( α v, α 2, β 1, and β 3). Cell adhesion assays with rat osteoclasts and affinity chromatography/SDS-PAGE analysis with purified human osteoclast membranes demonstrated adhesion of osteoclasts to native type I collagen in a divalent cation and Arg-Gly-Asp (RGD)-dependent way via α 2β 1 integrin, whereas osteoclast adhesion to denatured collagen predominantly involved α vβ 3. In receptor-binding assays, the involvement of human recombinant α vβ 3 in adhesion to denatured collagen was confirmed. Additionally, osteoclasts adhered to type I collagen fibers and to monomeric types II–V collagen with characteristics similar to those on native monomeric type I collagen. ] Osteoclastic bone resorption in vitro was inhibited (>40%) in the presence of α2 and β 1 antibodies. Using scanning laser confocal microscopy, α vβ 3, α 2, and β 1 integrin were detected within podosomes in nonresorbing osteoclasts and in the ruffled border area and basolateral membrane in resorbing osteoclasts, but not in the sealing zone of resorbing osteoclasts. These results demontrate that α 2β 1, in addition to α vβ 3, has an important role in osteoclast function and acts as a receptor for native, but not denatured, collagen.

Segment Substitutions in Alpha Satellite DNA: Unusual Structure of Human Chromosome 3-specific Alpha Satellite Repeat Unit

We have sequenced the full-length copy of the alpha satellite higher-order repeated unit characteristic of human chromosome 3. Its internal structure, the regular alternations of J1 and J2 type monomers, is typical of the alphoid suprachromosomal family 1. This dimeric order is disrupted by the substitution of one J1 unit by an alien dimer which is not clearly related to any of the established monomeric types. We have also observed some other similar cases of segment substitutions in alpha satellite DNA. They probably represent a special type of molecular event which could be generated by gene conversion. Segment substitutions may be one of the important factors responsible for the extreme variability of localization patterns and actual sequences of alpha satellite DNA that should be taken into account in reconstructions of alpha satellite evolution.

Rock impregnation trials using monomers, epoxide, and unsaturated polyester resins

ABSTRACT Impregnation of very small pores and cracks in large specimens calls for impregnating materials of the maximum fluidity. Recent trials showed that monomeric types of impregnating material give considerably better penetration than the epoxides and polyesters usually used for this purpose. The monomers and their resulting polymers have, however, certain disadvantages compared with the more standard impregnating media. The advantages and problems associated with monomer impregnation are discussed and details are given of a simple impregnation technique employing the monomer styrene.