title: Genetic synthesis and characterization of pH- and temperature-sensitive silk-elastinlike protein block copolymers.
abstract: The purpose of this work was to synthesize and characterize a pH- and temperature-sensitive block copolymer containing repeating sequences from silk (Gly-Ala-Gly-Ala-Gly-Ser) and elastin (Gly-Val-Gly-Val-Pro) protein. The monomer contained one repeat of silk and eight repeat units of elastin, with the first valine in one of the elastin repeats being replaced by glutamic acid. The copolymer was synthesized using genetic engineering techniques. The sensitivity of the copolymer to pH and temperature was examined at various polymer concentrations and ionic strengths. Turbidity measurements were carried out over a temperature range of 20 to 100 degrees C at various pH, concentration, and ionic strength values. The introduction of an ionizable residue (glutamic acid) rendered the copolymer sensitive to changes in pH. The transition termperature (T(t)), the temperature at which the polymer became insoluble upon increase in temperature, was modulated by changing the pH. In general, the T(t) value, was found: (1) to increase with an increase in pH, (2) to decrease with increasing ionic strength, and (3) to decrease with increasing concentration. Results of these studies suggest that by strategic placement of charged amino acids in genetically engineered silk-elastinlike protein block copolymers it is possible to precisely control sensitivity to stimuli such as pH and temperature.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201, USA.
authors.forename: Ashish
authors.initials: A
authors.lastname: Nagarsekar
authors.forename: John
authors.initials: J
authors.lastname: Crissman
authors.forename: Mary
authors.initials: M
authors.lastname: Crissman
authors.forename: Franco
authors.initials: F
authors.lastname: Ferrari
authors.forename: Joseph
authors.initials: J
authors.lastname: Cappello
authors.forename: Hamidreza
authors.initials: H
authors.lastname: Ghandehari
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry / Q000235:genetics; D011088:DNA Ligases / Q000378:metabolism; D004549:Elastin / Q000737:chemistry / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D019476:Insect Proteins / Q000235:genetics*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D047011:Silk; D013696:Temperature; D014169:Transformation, Bacterial
chemical_list: D019476:Insect Proteins; D009841:Oligonucleotides; D011108:Polymers; D011994:Recombinant Proteins; D047011:Silk; D018698:Glutamic Acid; D004247:DNA; D004549:Elastin; D011088:DNA Ligases