Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Homopolymers”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMed1990

Degradation of N5-(2-hydroxyethyl)-L-glutamine and L-glutamic acid homopolymers and copolymers by papain.

The rate of degradation of poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG), poly(L-glutamic acid) (PGA) and poly[HEG-co-GA] random copolymers by papain was measured in the pH range 4.0-7.5, employing the gel permeation chromatography method. The effect of the degree of ionization on the polymer conformation was measured by circular dichroism (c.d.). PHEG, which is uncharged, had a random coil conformation and an almost constant degradation rate within the whole pH interval. The ionization of PGA increased with increasing pH and was accompanied by conformational transition from helix to random coil. The hydrolysis of PGA by papain depended on pH with the optimum at about pH 5, indicating that both the high content of helix (at pH less than 5) and increasing charge density (at pH greater than 5), decreased the degradation rate. Contrary to PGA, pH profiles of the degradation rate of poly[HEG-co-GA] copolymers are monotonous and do not decrease at pH less than 5. In the copolymers the HEG residues act as a helix breaker and limit the formation of helical conformation. The role of structural features of a macromolecular substrate, i.e. the charge, helical conformation and the nature of amino acid residues, in the interaction between enzyme and polymer is discussed.

Chromatography, Gel↗
PubMed1983

A homopolymer of the potent antitumor drug 2'-deoxy-5-fluorouridylate.

Poly(5-fluoro-2'-deoxyuridylic acid) was synthesized and its properties were compared with those of poly(dT) and poly(dU). It readily complexed with poly(dA). The 1:1 complex melted at about 20 degrees C lower than poly(dA) . poly(dT). A triple-stranded helix, poly(dA) . 2 poly(dF5U) was formed only in high salt (2.0 M NaCl).

Chemical Phenomena↗
PubMed2005

Sequential design of a novel PVA-based crosslinked ethylenic homopolymer for extended drug delivery.

A Box-Behnken Design was employed to study the influence of boric acid, sodium sulfate, ammonia and n-propanol in the formulation of crosslinked ethylenic homopolymeric (CEH) gelispheres from native polyvinyl alcohol (PVA). The dependent variables studied included the size of the spherical gelispheres, drug encapsulation efficiency, in vitro dissolution after 30 min and textural parameters, namely fracture force and matrix rupture energy. Based on these responses, an optimized CEH gelisphere matrix was formulated and thereafter incorporated as a powder into a candidate crosslinked zinc-pectinate multiple-unit device to assess its effect on modifying drug release. In the case of the CEH-loaded zinc-pectinate gelispheres, it was determined via constrained optimization that a maximum drug encapsulation efficiency of 28.63% could be obtained under the conditions of 0% (w/v) CEH, 13 h of crosslinking and drying temperature of 60 degrees C. On the other hand, initial drug release could be significantly retarded when 0.10% (w/v) of CEH was included in the formulation and crosslinked for 24 h at 40 degrees C. In this regard, CEH induced a 4 h lag phase. Furthermore, zero-order drug release was produced and could be maintained over several weeks. Kinetic analysis of drug release further supported that CEH inhibits polymer relaxation (k2<<k1), and hence slows down drug diffusion. Based on these results, the CEH-zinc-pectinate drug delivery system appears to be a suitable carrier that may be employed for long-term administration for, e.g. via subcutaneous implantation.

1-Propanol↗
PubMed1999

Microsecond time-scale discrimination among polycytidylic acid, polyadenylic acid, and polyuridylic acid as homopolymers or as segments within single RNA molecules.

Single molecules of DNA or RNA can be detected as they are driven through an alpha-hemolysin channel by an applied electric field. During translocation, nucleotides within the polynucleotide must pass through the channel pore in sequential, single-file order because the limiting diameter of the pore can accommodate only one strand of DNA or RNA at a time. Here we demonstrate that this nanopore behaves as a detector that can rapidly discriminate between pyrimidine and purine segments along an RNA molecule. Nanopore detection and characterization of single molecules represent a new method for directly reading information encoded in linear polymers, and are critical first steps toward direct sequencing of individual DNA and RNA molecules.

Bacterial Toxins↗
PubMed2000

Electromigration of polyion homopolymers across biomembranes: a biophysical model.

The analysis of polyion transmembrane translocation was performed using membrane electrical equivalent circuit. The dependence of polyion flux across membranes on time, membrane electrical conductance, membrane electrical capacitance, degree of polymerization, water solution conductance and applied transmembrane potential is discussed. The changes in polyion flux were up to 88% after 1 ms. Both the increase of polyion chain length and the decrease of membrane conductance resulted in the diminution of this effect. Inversion of flux direction was observed as a result of external potential changes. Reversal curves, representing the values of considered parameters for zero-flux were also shown. The replacement of a polyanion by a polycation of the same chain length resulted in the same shape of the surface plot but with opposite orientation. The analysis describes the effect of transmembrane potential on the translocation rate of polyanionic polysialic acid and polynucleotides, and polycationic peptides across membranes.

Biological Transport, Active↗
PubMed2000

Chemical grafting of molecularly imprinted homopolymers to the surface of microplates. Application of artificial adrenergic receptor in enzyme-linked assay for beta-agonists determination.

A technique for coating of microplate wells with a molecularly imprinted polymer (MIP), specific for epinephrine, is presented. 3-Aminophenylboronic acid was polymerized in the presence of epinephrine using oxidation of the monomer by ammonium persulfate. This process resulted in the grafting of a thin polymer layer onto the polystyrene surface of the microplates. The polymer affinity was determined by an enzyme-linked assay using a conjugate of horseradish peroxidase and norepinephrine (HRP-N). It was found that imprinting resulted in increased affinity of the polymer toward HRP-N and epinephrine. Influence of the buffer pH and concentration on the polymer affinity was analyzed. It was shown that the MIP-coated microplates could be used for assay development and drug screening. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to traditional antibodies or receptors, used in ELISA.

Adrenergic beta-Agonists↗
PubMed1993

Separation of amino acid homopolymers by capillary gel electrophoresis.

Gel-filled capillaries utilizing highly concentrated and moderately cross-linked acrylamide-type gels in capillary electrophoresis were successfully applied to the separation of the individual oligomers of various poly(amino acids). Mixtures of both anionic and cationic nature were adequately resolved. While UV detection at 220 nm was mostly utilized, the polyanions with N-terminal groups can also be tagged with 3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde (CBQCA) for a more sensitive detection by a laser-induced fluorescence detector.

Amino Acids↗