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Home PageOnline Product Catalog > Custom Peptides & Small Molecule > Peptide Libraries

Custom Peptide Library Services
 
GSI has been offering custom peptide and other services for the last 20-yrs. There are 1000s of publications in peer-reviewed journals using GSI peptide services. GSI offers the most competitive price quote without compromising the quality of services. GSI services include:
 
·         Free expert consultation to produce peptide library
·         Peptide range 5-20 amino acids or as desired
·         Peptide scale 1-10 mg per peptide or as desired
·         Peptide purity Crude to >95% or as desired.
·         Peptide modifications (Biotin, FITC, or unnatural amino acids etc)
·         No cross contamination
·         Full QC (mass spec, hplc on all purified peptides)
·         Standard turnaround ~2-4 weeks.
 
 
Custom Peptide Library-General Information
 
What is peptide Library and its applications?
 
A peptide library is a new technique for studying structure-function relationship for a protein. A peptide library contains a great number of peptides that have a systematic combination of amino acids. The peptide library provides a powerful tool for drug design, protein-protein interactions, and other biochemical as well as pharmaceutical applications. It also has wide applications in drug screening, target validation, epitope mapping, and vaccine development. Some other applications of peptide library are:
  • Receptor (GPCR) ligand screening
  • Peptide Drug discovery
  • Protein-Protein interaction
  • Functional proteome
  • Peptide-Nucleic acid binding
  • Enzyme substrate or Peptide-Inhibitor screening
  • Antigen binding sites or epitope mapping
  • T-Cell epitope disovery
  • Antoantibody binding sites on antigens (protein)
  • Antibody cross reaction with a related protein family member
  • Identification of small peptides as vaccine candidates
How peptide libraries are made and peptide specifications?

Usually, peptide library is synthesized on solid phase, mostly on resin, which can be made as flat surface or beads.  Peptides are eluted off the resin and supplied as either crude peptides or desalt, >70%, >85%, and >95%).  Peptides can be made in required amounts from minimal to mg scale for initial screening.  Appropriate peptide labels (Biotin, FITC etc) can be added upon request. Each peptide in the library undergoes rigorous quality control to avoid any cross contaminants before delivery. All purified peptides are delivered with complete QC data including RP-HPLC, MS, and COA report to ensure high quality.  Peptide length in a given library is usually 5-20 aa with 1-5 amino acid overlap.

Peptide Library Types and applications

Depending upon a given application, peptide libraries are usually defined as:
A. Overlapping Peptide Library
Overlapping peptide library can be used for epitope mapping. The peptide length (5-20 aa) and offset number or the degree of overlapping amino acids (2-5 aa) is determined by the length of the full length proteins, overall experiment objectives and the cost. As a general guideline, shorter peptides have less chances for multiple epitope hits. Greater degree of overlapping (small offset number) gives more chances of multiple epitope hits.
Example:   (peptide length 10 aa, offset/overlap 7 aa)
        DSTRKLMNRT QSEDKLPSRG QHTRSDKENN PSSTRGHLED (30 aa protein)
        DSTRKLMNRT                      Peptide #1
           RKLMNRTQSE                  Peptide #2
              MNRTQSEDKL               Peptide #3
                 TQSEDKLPSR             Peptide #4
Total peptides, n=11
 
A) A. Alanine Scanning Library

Example:   (peptide length 10 aa)
        DSTRKLMNRT                      Peptide #1
        ASTRKLMNRT                      Peptide #2
        DATRKLMNRT                      Peptide #3
        DSARKLMNRT                     Peptide #4
        DSTAKLMNRT                      Peptide #5
        DSTRALMNRT                      Peptide #6
        DSTRKAMNRT                     Peptide #7
        DSTRKLANRT                      Peptide #8
        DSTRKLMART                      Peptide #9
        DSTRKLMNAT                      Peptide #10
        DSTRKLMNRA                     Peptide #11
 
B. Truncation Library

Truncated peptide library can be used to identify the shortest amino acid sequence needed for a given function or activity.  
Example:   (peptide length 10 aa) Truncation from the N-terminus
        DSTRKLMNRT              Peptide #1 (control peptide with full function)
         STRKLMNRT               Peptide #2
         TRKLMNRT               Peptide #3
           RKLMNRT                Peptide #4
            KLMNRT         Peptide #5
             LMNRT          Peptide #6
              MNRT          Peptide #7
Truncated peptides can also be generated from the C-Terminus.
 
C. Random/scrambled Library

Scramble Library is constructed by carrying out permutation on the original peptide’s sequence. The number of each amino acid (e.g, 2 Arg or R) is the same in the peptide except its postion and other amino acids are created at random. This strategy is used for preliminary identification of a group of active sequences that may possess a given function or activity. 
        DSTRKLMNRT              Peptide #1 (control peptide with full function)
        TRLKSTNRMD              peptide # 2
        RSTRLDMNKD             peptide # 3 etc
 
Positional Scanning Library

A selected position or positions in a peptide sequence are each systematically replaced with all other natural amino acids (20) or any other amino acid to determine the preferred amino acid residues at a given position that will maximize the peptide activity.
Example:   (peptide length 10 aa, with substitution of “K at postion 5.
        DSTRKLMNRT                      Peptide #1 (control peptide)
        ASTRALMNRT                      Peptide #2
        ASTRCLMNRT                      Peptide #3
        ASTRDLMNRT                      Peptide #4
        ASTRELMNRT                      Peptide #5
        ASTRFLMNRT                      Peptide #6
        ASTRGLMNRT                      Peptide #7
Potential peptides =20 with all 20 natural amino acids. It is also possible to study the replacement of “N” at position #8.



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