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Effect of ionic strength on folding and aggregation of the hemolytic peptide melittin in solution

H Raghuraman1, Amitabha Chattopadhyay

  • 1Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.

Biopolymers
|May 9, 2006
PubMed

Insights

Red edge excitation shift (REES) effectively monitors melittin aggregation dynamics. This fluorescence method tracks changes in melittin

Area of Science:

  • Biochemistry
  • Biophysics
  • Analytical Chemistry

Background:

  • Melittin, a 26-amino acid peptide, is known for its hemolytic activity, attributed to its amphipathic and cationic nature.
  • Melittin exhibits intrinsic fluorescence due to a tryptophan residue, crucial for its biological functions.
  • While melittin's aggregation is known, dynamic aspects of this process, especially under varying ionic strengths, remain underexplored.

Purpose of the Study:

  • To investigate the effect of ionic strength on the dynamics and aggregation behavior of melittin in aqueous solutions.
  • To evaluate the utility of the red edge excitation shift (REES) fluorescence approach for monitoring melittin self-association.

Main Methods:

  • Utilized sensitive fluorescence spectroscopy techniques, including the red edge excitation shift (REES) approach.
  • Employed fluorescence emission maximum, polarization, and lifetime measurements to probe environmental changes around tryptophan.
  • Conducted fluorescence quenching experiments with acrylamide and trichloroethanol to assess tryptophan accessibility.
  • Performed circular dichroism (CD) spectroscopy to confirm structural changes.

Main Results:

  • Demonstrated that REES is sensitive to ionic strength-induced self-association of melittin.
  • Observed changes in fluorescence emission maximum, polarization, and lifetime correlating with melittin's altered environment.
  • Confirmed ionic strength-induced alterations in melittin's secondary structure via CD spectroscopy.
  • Quenching experiments provided insights into the accessibility of the tryptophan residue during aggregation.

Conclusions:

  • Established REES as a sensitive method for monitoring melittin aggregation dynamics influenced by ionic strength.
  • The study provides the first evidence for REES's applicability in tracking protein and peptide aggregation.
  • These findings offer a new tool for understanding dynamic processes in peptide and protein solutions.

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