ISSN:
1573-904X
Keywords:
peptide stability
;
liquid crystal formation
;
birefringence
;
surface tension
;
luteinizing hormone-releasing hormone (LHRH)
;
hydrolysis
;
aggregation
;
micelles
;
surface activity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The degradation of native LHRH in aqueous buffers of pH ∼1–10 obeyed the rate equation, k obs = k H + a H + + k o + k HO-(a HO-) x , where x at 60–100°C was ∼0.64 and temperature independent. Extrapolation to 25°C using the Arrhenius equation and secondary rate constants showed that native LHRH is reasonably stable at pH 5.4, giving a shelf life (t 90) of approximately 5 years. Regarding physical properties, hydrophobic LHRH analogues nafarelin and detirelix were found to be surface active as demonstrated by a decrease in apparent surface tension with increased peptide concentration. The CMC for detirelix at pH 7.4 was determined to be 5.3 × 10−4 M (0.88 mg/ml), and that for nafarelin, 〉2 mg/ml. At higher concentrations (∼4–8 mg/ml), nafarelin and detirelix formed nematic liquid crystals of undulose extinction (birefringence, 〈0.001). The thermo-dynamic stability of these peptide liquid crystals was probed by determining their melting points (T cm) in the presence of propylene glycol, a solvent which proved to be efficacious at suppressing gelation and at destabilizing liquid crystals as measured by a reduction in T cm.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1015847628047
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