Voltammetric Study of Poly Aspartic Acid-Cd2+ and/or Zn2+ Complex in the Helix-coil Transition pH Region
Author(s):
Abstract:
Helix-coil transition of poly aspartic acid (PASP) was investigated by dc polarography in the presence of Cd2+ and/or Zn2+ as a detecting marker which attached to the polymer. The diffusion currents (id) of Cd2+ and Zn2+ decreased sharply in the pH range of 3.5-7.0 due to the formation of the metal ions-PASP macromolecular complexes. The complex formation revealed on an increase in the magnitude at 222 nm of CD spectrum of the polymer, indicating that PASP forms helix structure by coordination of both ions in the corresponding pH region. The helix content of PASP, estimated by polarography is in good agreement with that by CD in neutral pH region. The degree of helicity induced by either of these two ions also can be determined independently by polarography. The size of the complex was calculated by Ilkovic’s equation and depends on strongly mixing ratio of PASP residue to cation marker. On the other hand in the lower acidic pH region, the coordination mode of these ions to PASP is different from that at neutral pH region. The decreases in id of the ions are independent of the further formation of helix structure. The metal ions coordinate with sparsely dissociated carboxylate groups of helical part of PASP, which bring about an aggregation of polypeptide strands. The diffusion current of the metal ion attached to the polymer, therefore, is a parameter sensitive to a conformational change of PASP from acidic through neutral pH region.
Keywords:
Language:
English
Published:
Analytical & Bioanalytical Electrochemistry, Volume:7 Issue: 4, Aug 2015
Page:
494
magiran.com/p1445198
دانلود و مطالعه متن این مقاله با یکی از روشهای زیر امکان پذیر است:
اشتراک شخصی
با عضویت و پرداخت آنلاین حق اشتراک یکساله به مبلغ 1,390,000ريال میتوانید 70 عنوان مطلب دانلود کنید!
اشتراک سازمانی
به کتابخانه دانشگاه یا محل کار خود پیشنهاد کنید تا اشتراک سازمانی این پایگاه را برای دسترسی نامحدود همه کاربران به متن مطالب تهیه نمایند!
توجه!
- حق عضویت دریافتی صرف حمایت از نشریات عضو و نگهداری، تکمیل و توسعه مگیران میشود.
- پرداخت حق اشتراک و دانلود مقالات اجازه بازنشر آن در سایر رسانههای چاپی و دیجیتال را به کاربر نمیدهد.
In order to view content subscription is required
Personal subscription
Subscribe magiran.com for 70 € euros via PayPal and download 70 articles during a year.
Organization subscription
Please contact us to subscribe your university or library for unlimited access!