I tried measure concentration of peptide LL-37 by methods (BCA, Bradford), but i am not successful. Concentration values very low comparble with expected values. There is another method to measure?
Or maybe problem is solubility of LL-37? I have LL-37 in this buffer (25 mM Tris, 100 mM NaCl, 2 mM DTT, pH = 8,5).
Thank you for answer...
According to the Anaspec datasheet for this peptide, it is freely soluble in water. Your buffer should be fine.
Because it is a relatively small peptide compared to the usual protein standards used for colorimetric protein assays, such as BSA, the standard may not represent the response to the peptide accurately. You could send a sample for quantitative amino acid analysis to a service lab to get an accurate concentration, then use that value to calculate a correction factor for your colorimetric assay standard curve.
However, check in the literature first to see how the concentration has been quantified by others. Here are some references on LL-37 from Anaspec:
https://www.anaspec.com/products/product.asp?id=38583
Well, for different samples, the performance of these methods is usually evaluated being a well-established protocol. For instance, the detection range of Smith BCA would be about 0.2-50μg in the solvent, though the substrate was stabilized under an alkali condition. Then, its sensitivity could be increased at 60°C compared to room temperature. Unlike Smith BCA, Bradford method develops color under an acidic condition, where arginine, lysine, histidine, tyrosine, tryptophan, and phenylalanine residues are the primary targets to dye reactions. So, to address your concern, both of the sequence traits and dispersion stability of the assayed peptide in the buffer should be well examined.
Good luck.
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