ProtParam

ProtParam computes physical and chemical parameters from a protein amino acid sequence, including sequences derived from two-dimensional (2-D) gels, to support protein characterization and experimental planning.

Key Features:

• Molecular Weight: Determines the mass of the protein from its amino acid sequence.
• Theoretical pI (Isoelectric Point): Predicts the pH at which the protein carries no net electrical charge to aid separation and purification.
• Amino Acid Composition: Provides the frequency distribution of each amino acid within the sequence.
• Atomic Composition: Reports the number of atoms of each element present in the protein sequence.
• Extinction Coefficient: Estimates how much light the protein absorbs at a specified wavelength for concentration measurements.
• Estimated Half-Life: Predicts the temporal stability of the protein for experimental planning.
• Instability Index: Assesses the probability that a protein will be stable or unstable in vitro.
• Aliphatic Index: Measures the relative volume occupied by aliphatic side chains (alanine, valine, isoleucine, leucine) as an indicator of thermostability.
• Grand Average of Hydropathicity (GRAVY): Calculates the average hydrophobicity or hydrophilicity of the protein to inform solubility and interaction tendencies.

Scientific Applications:

• Protein Identification from 2-D Gels: Supports matching of experimentally observed protein spots to theoretical parameters such as molecular weight and pI.
• Experimental Design and Planning: Informs sample handling, stability assessments, and storage decisions using estimated half-life and instability index.
• Purification and Separation Strategy: Guides choice of conditions for chromatographic or electrophoretic separation based on theoretical pI and molecular weight.
• Quantitative Protein Measurement: Enables estimation of protein concentration from absorbance data using the extinction coefficient.
• Thermostability and Solubility Assessment: Provides indicators of thermostability (aliphatic index) and solubility/interaction propensity (GRAVY) for downstream experiments.

Methodology:

Calculates listed physico-chemical parameters from an input amino acid sequence and leverages information from protein databases.