CD (circular dichroism) is a powerful experimental method for determination of
the 2nd structures of peptides and proteins in solution. The percentage of alpha
helix, beta sheet and random coil in a peptide can be quantitatively determined
according to its CD spectrum.

Service and Price

Single point reading (catalog #: CD101)
CD signal intensity at 222 nm or 215 nm.
Result reported in molar ellipticity (mean residue ellipticity).
Price: Email us for a quote
Peptide amount: 5 mg

Full spectrum collection (catalog#: CD102)
CD spectrum from 190 nm to 260 nm
Price:Email us for a quote
Peptide amount: 5 mg

Five concentration TFE titration (catalog# CD103)
Full spectra from 190 nm to 260 nm recorded in 0, 20, 40, 60 and 80% TFE
Price: $285.00 per sample, spectra collection only
           $385.00 per sample, spectra collection and data analysis
Sample amount: 10 mg

Sample Requirement

Peptide purity            >95%
Peptide amount          experiment depentent (see above)
Peptide length            no limitation

since concentration is critical for quantitative determination of the 2nd structure of a peptide, it is very helpful if your peptide has a Tyr or Trp in the sequence. This allows the concentration of the peptide to be accurately determined by spectroscopy method. For the peptides that do not have an internal Tyr or Trp, we suggest you to add a Tyr at the either end of the peptide. If you experiments do not allow to add an extra residue, please to send us at least 5 mg sample to minimize the error introduced by weighing.

• All CD services include sample preparation and peptide concentration determination
• 4 repeat scans are performed for each sample. The final spectrum is the average of the 4 scans
• All peptide samples should be sent to us as lyophylized powder
• peptide samples will be discarded after experiment. If you want your peptide be sent back to you, please add $25.00 for CD101 and CD102 and $40.00 for CD103.
• 10% discount will be offered if peptides are ordered from us
• we provide contract research of using CD to study peptide or protein structure, stability, ligand-protein interaction, effect of mutation on the conformation and others. Please email us your project. We will send you a free evaluation..
Peptide CD and TFE Titration
TFE (triflluoroethenol) is well know for its ability to promote alpha helix formation. Many peptides that show random coiled CD spectra in aqueous solution become helices when TFE is added. The extent of the helical structure in a given amount of TFE depends on the sequence. For two peptides that both show little helical structure in aqueous buffers, one could show higher helical structure in TFE. The intrinsic helical propensity ( or the stability of helical structure) of a peptide can be determined by record a series of CD spectra as a function of TFE concentration.
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