1, How to choose the most suitable purity for peptides? (peptide application).
Generally speaking,different purity ,then different prices for the peptides of the same sequence ,quantity and modified：higher purity, the higher price for the unit mass of peptides. Bankpeptide can provide crude, desalination, 70% to 99% purity peptides with different purity levels for customers to choose according to their needs
The purity and application of various peptides are follows:
Crude peptide:
Large scale functional screening
Desalination, >70% and >75% peptides:
Animal immunization and preparation of polyclonal resistant serum
The concentration of antibody was determined by ELISA.
>80%, >85% and >90% peptides:
Study of non quantitative enzyme substrate
Phosphorylation studies
Western blotting non quantitative study, immunohisto chemical study and vitro biological detection
Binding to the chromatographic resin by affinity chromatography
used as a cell attachment of culture plate; protein electrophoresis
>95% and >98% polypeptide:
Standard quantitative operation of ELISA and RIA
Quantitative study on receptor / ligand interactions
Vitro biological assay in cell
Vivo study of cell
Quantitative closure and competitive detection
Quantitative study of protease
Enzymatic studies
Chromatographic standard
Nuclear magnetic resonance study
Production of monoclonal antibodies
2, How to save the freeze-dried peptides ?
(1) All of the lyophilized peptides can transport avoiding light at room temperature and can preserved under the condition of room temperature days or less than a week. The peptide traits are stable. All the lyophilized peptide products must br stored in low temperature (- 20 DEG C is better) and drying conditions. If it is possible, - 80 DEG C is the best. Under such conditions, most of peptides can be preserved for 1-2 years.
(2).When the peptide products need to be used,the temperature of products should be risen to room temperature before opening the cover.
(3). For the easily oxidized peptides whose sequences containing Cys, met, try and the degradable peptides which contain Gln, ASN, ASP, repeated freezing and thawing should be avoided.
(4)For temporarily non used peptides, please do not save in the form of a solution (even at -80 DEG C conditions).
3, How to dissolve the peptides and preserve the peptide solution?
The following principles should be followed:
(1).Saving by a small package, So it is easy to thaw according to needs then discard the remainder.
(2).The most peptides can be dissolved by buffer water or pH5~7 as solvent, being stored at -20 deg.c for several days.
(3). For the hydrophobic insoluble peptides , first please dissolve in organic solvents (DMF, DMSO), again with water or with pH 5 ~ 7 buffer diluted to an appropriate concentration; but for those easily oxidized peptides which contain Cys, met, try, please don’t use DMSO as solvent.
(4)For the easily oxidized peptides whose sequences containing Cys, met, try and the degradable peptides which contain Gln, ASN, ASP , it is not strongly recommended to save in the solution state.
4.How to choose the appropriate fluorescence labeling groups How to Choosing the appropriate fluorescence labeling groups depends on the needs of your experimental. Experimental studies on pharmacology based in two categories: vivo and vitro study. For vivo studies, the general choice of emission wavelength fluorophores is in 650-900nm. For example: ICG, cy5.5 and Nile blue. For vitro studies, the emission wavelengths between 400 to 600nm are most commonly used, for example, AMC, FITC, and TAMRA.
5, The cause of the instability of the peptides
(1)free amide reaction
(2).There are two main reasons for the oxidation of peptide solution. One is the contamination of peroxide in solution, and another is the spontaneous oxidation of peptides.
(3).The hydrolysis and fracture of peptide bonds.
(4)Forming wrong disulfide bridge bonds.
(5)Racemization
(6)β-remove.
(7). Denaturation, adsorption, aggregation or precipitation are generally related to the destruction of the three stage structure and the two stage structure.
6, The way to improve the stability of peptides
1) fixed point mutation
Replacing residues which can lead to the instability of the peptides by genetic engineering or adding residues which can increase the stability of the peptide.
2) chemical modification
There are many chemical modification methods of peptide , PEG modification is the common one in the research.
3) additive
By adding additives such as sugar, polyol, gelatin, amino acid and some salts, which can improve the stability of the peptides .
4) lyophilization
