{"id":1015,"date":"2023-09-29T00:44:44","date_gmt":"2023-09-28T16:44:44","guid":{"rendered":"https:\/\/molchanges.com.wpcmsx.com\/?page_id=1015"},"modified":"2025-05-21T12:01:24","modified_gmt":"2025-05-21T04:01:24","slug":"faq","status":"publish","type":"page","link":"https:\/\/molchanges.com\/zh\/faq","title":{"rendered":"\u5e38\u89c1\u95ee\u9898"},"content":{"rendered":"\t\t
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Frequently Asked Questions<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Simply to Complex from Milligrams to Kilograms<\/p>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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\n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tCustom Quote Request<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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\n \n \n How to store peptides?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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Lyophilized Peptides<\/p>

For long-term storage of peptides, we recommend storing them as a solid powder. Lyophilized peptides can be stored at -20\u00b0C or lower with minimal degradation. Customers are advised to re-inspect customized peptides every 2 years from the date of quality control release.<\/p>

Peptides in solution<\/p>

Peptides in solution are less stable and prone to degradation. Aqueous solutions used to dissolve peptides should be sterile and pure.<\/p>

In solution, a certain amount of peptide may be degraded, depending on the amino acids present in the sequence. Some examples are listed below:
- Peptides containing methionine, cysteine or tryptophan residues should have limited storage time in solution due to oxidation. These peptides should be dissolved in an oxygen-free solvent. -
Glutamine and asparagine can be deamidated to glutamic acid and aspartic acid, respectively. -
Cysteine can undergo oxidative cyclization to form a cysteine-cysteine disulfide bond (which can be formed within or between disulfide bonds). -
The charged residues (aspartic acid, glutamic acid, lysine, arginine, histidine) are hygroscopic (absorbing water from the air) and tend to form a viscous, clear oil. This physical change may not affect the nature of the peptide. It is recommended that such peptides be lyophilized to remove trace amounts of water, then degassed with nitrogen to ensure that there is no water vapor in the vial, and then quickly capped.<\/p>

To prevent damage from repeated freezing and thawing, we recommend that users only dissolve the amount of peptide required for the current experiment. Excess solution should be stored at \u2265 -20 o C until needed.<\/p>

Avoid moisture.
Since moisture significantly reduces the long-term stability of peptides, we recommend equilibrating the peptides in a desiccator to room temperature before opening the vials. Upon completion of peptide dispensing, the remaining peptides in the tube should be gently purged with anhydrous nitrogen, then the container should be capped, sealed with a sealing film, and stored at -20\u00b0C.<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n How do you dissolve peptides?<\/span>\n\n \n
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The solubility characteristics of different peptides vary considerably. Residues such as alanine (Ala), cysteine (Cys), isoleucine (Ile), leucine (Leu), methionine (Met), phenylalanine (Phe), and valine (Val) add to the peptide's hydrophobicity and solubility in aqueous solutions, and it is recommended that the customer follow these guidelines when customizing peptides.<\/p>

Solubility Properties<\/p>

The solubility of peptides is highly dependent on the amino acid sequence. Naturally hydrophobic peptides (A, F, G, V, L, I, M, W, P with higher propensity) require organic solvents for solubilization. Acidic peptides (higher propensity for D, E in the peptide sequence) require basic aqueous buffers for solubilization, while basic peptides (higher propensity for K, H, and R) require acidic aqueous buffers for solubilization.<\/p>

Solvent Selection<\/p>

Given the limitations of your assay, we recommend using the following guidelines to determine the best solvent for solubilizing peptides<\/p>

\u00a0<\/p>

Hydrophobic Peptides<\/p>

To re-solubilize hydrophobic peptides, add 100 \u00b5L of DMSO and sonicate until a homogeneous solution is formed. Next, add the buffer of your choice to make a 1 mg\/mL solution (the higher the peptide concentration, the greater the amount of DMSO required).<\/p>

\u00a0<\/p>

Hydrophilic (Acidic) Peptides<\/p>

To re-solubilize acidic peptides, add 100 \u00b5L of 1% NH 4 OH to 1 mg of peptide and vortex. Once the solution is clear, add the buffer of your choice to make a 1 mg\/mL solution.<\/p>

Hydrophilic (Basic) Peptides<\/p>

To reconstitute a basic peptide, add distilled water to 1 mg of peptide and vortex.<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n What is the difference between net vs gross peptide weight?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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The industry standard is to deliver peptides in a lyophilized form as a Gross weight.\u00a0Gross peptide weight<\/b>\u00a0is the total weight of all components present in the lyophilized powder. This includes the peptide of interest, any peptide impurities, water, residual solvents, and counterion.<\/p>

On the contrary\u00a0Net<\/i>\u00a0peptide weight<\/b>, calculated from the\u00a0Net peptide content<\/b>, is the weight of\u00a0only the peptide<\/i>\u00a0component present in the lyophilized powder. This offers more accurate concentrations of your subsequent peptide solutions. Hence, we recommended net peptide weight amounts for\u00a0Custom Peptide<\/b>\u00a0orders.<\/p>

\"Net<\/p>

Net Peptide Content<\/b>\u00a0measurement is performed by amino acid analysis (AAA; limited accuracy but requires a low material amount) or elemental analysis (CHN; requires milligrams of peptide but is more accurate). Both methods yield a percentage value (ie., 75% net peptide content).<\/p>

The Net Peptide Content depends on the amount of counterion present*, which is dependent on the peptide sequence. Essentially, the higher the peptide charge, the lower the peptide content<\/p>

*Note: The element used to calculate net peptide content is based on the peptide counter-ion. This is done to ensure that the counter-ion does not contribute to the peptide content amount. For example, when TFA or acetate are the counter-ion, nitrogen is used because it is found in the peptide but not in TFA or acetate. Carbon or Nitrogen can be used used when chloride is the counter-ion for the same reason.<\/p>

Net Peptide Weight calculations:<\/h4>

Net Peptide Quantity (total peptide)<\/b>\u00a0\u2014 method we use for net custom peptide orders.<\/p>

Multiply the Net Peptide Content Percentage (decimal form) by the Peptide Gross Weight, to obtain the amount of Net Peptide Quantity (total peptide).<\/p>

For example:
For 5 mg gross peptide\/vial:
Peptide net content is 84%.
Exact amount of total peptide = 0.84*5 mg=4.2 mg total peptide<\/p>

Net Peptide of Interest Quantity\u2014most accurate<\/b>\u00a0\u2014 customer can use this method on their own to calculate peptide of interest.<\/p>

Multiply Net Peptide Content Percentage by the Peptide Gross Weight, and the Peptide Purity (by HPLC), to calculate the exact amount of the peptide of interest you have. The net peptide percent (decimal form) is multiplied by peptide purity (decimal form).<\/p>

For example:
For 5 mg gross peptide\/vial with:
Peptide net content is 84%.
Exact amount of peptide of interest is = 0.84*0.96*5 mg=4.03 mg<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n What type of chemistry do you use?<\/span>\n\n \n
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MOL Changes utilizes solid-phase Fmoc chemistry rather than BOC chemistry. Fmoc chemistry allows for the removal of protecting groups using mild conditions during peptide elongation, while BOC chemistry requires the use of a strong acid to remove the protecting groups during peptide elongation.\u00a0 Additionally, Fmoc chemistry utilizes trifluoroacetic acid (TFA) to remove the peptide from the resin, while BOC chemistry utilizes hydrofluoric acid (HF).\u00a0 HF is colorless, highly corrosive, and a contact poison.\u00a0<\/p>

Therefore, MOL Changes employs Fmoc chemistry as it is more mild, flexible, and versatile compared with BOC chemistry.\u00a0\u00a0\u00a0\u00a0\u00a0<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n How do I calculate molarity of my peptide?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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Molarity refers to the molar concentration of a solution, which is the number of moles of solute dissolved in 1 liter of solution, expressed as mol\/L, or M.<\/p>

Molarity [M] = Mass \/ (Volume x Molar Mass); Mole = Concentration (g\/L) x Volume (L)\/MW (g\/mol)<\/p>

Example:
Given: 1mg of dry peptide powder with MW: 20KDa (Molar mass of peptide is 20 g\/mol)
To determine molarity with known mass and known volume
For a 1ml solution of this peptide:
Molarity = Mass (0.001g) \/ (volume (0.001L) x Molar Mass (MW 20,000) = 50\u03bcM<\/p>

To determine mass to achieve a certain molarity:
If for your assay, you need 0.01mM working peptide solution in 1ml of water, then calculate mass required as follows:<\/p>

Mass = Molarity x Volume x Molar Mass
Mass = 0.01mM x (1\/1000 L) x 20,000g\/mol = 0.0002g<\/p>

Hence, you will need 0.2mg\/ml of peptide to have a working solution of 0.01mM.<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n In what form are peptides delivered?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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We deliver as lyophilized or raw powder and peptide solution.<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n How do I know if my peptide will be soluble?<\/span>\n\n \n
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The solubility of a peptide in a given solvent is dependent on the amino acid sequence and often hard to predict.\u00a0 In the case of catalog peptides, the solubility information is listed on the QC datasheet.\u00a0 For custom peptides, please see the section entitled \"How should I solubilize my peptide\".<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n What is the difference between peptide content and peptide purity?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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Peptide content is not an indication of the peptide purity as these are two separate measurements. Purity is determined by analytical HPLC and indicates the presence\/absence of other peptidic contaminants (i.e. truncated peptides).<\/p>

Net peptide content determines the actual amount of the peptide (peptide of interest as well as the peptide contaminants) present in the sample. The net peptide content is traditionally measured by Amino acid analysis (AAA; limited accuracy but requires a low amount of material) or elemental analysis (CHN; requires milligrams of peptide but is more accurate).<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n How do you generally purify your peptides?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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MOL Changes peptides are generally purified by reverse-phase preparative HPLC, using 2 buffers containing 0.1% trifluoroacetic acid (TFA).\u00a0 The first buffer (Buffer A) is composed of 0.1 % TFA in deionized water and the second buffer (Buffer B) is composed of 0.1 % TFA in acetonitrile (ACN).<\/p>

Generally, crude peptides are first dissolved in a solution of either Buffer A, some amount of Buffer B, or an organic polar solvent such as DMSO.\u00a0 If an organic polar solvent or Buffer B was used, this clear solution will first be diluted with Buffer A. Next, the peptidic solution is filtered and loaded onto the preparative HPLC system.\u00a0 Utilizing an optimized method gradient, fractions are then collected based on the absorbance readings.\u00a0 Each fraction is then analyzed via an analytical HPLC to ensure that the purity of each fraction meets the required purity specification.\u00a0<\/p>

These \u201cpure\u201d fractions are then pooled together and lyophilized.\u00a0 The \u201cpure\u201d powder is then tested for both purity and identity to ensure that the correct peptide has been manufactured.<\/p>

Finally, an independent QC group at AnaSpec again tests the peptide to ensure that all of the testing attributes meet the required specifications.<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n How do I write my peptide sequence termini?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n <\/div>\n\n \n <\/a>\n <\/div>\n\n
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The international nomenclature used for the sequence termini is as follows:<\/p>

- N-terminus: H means free amine (NH2-), Ac means acetyl [CH3C(O)-NH-], Pyr means pyroglutamic acid
- C-terminus: OH means free acid (-COOH), NH2\u00a0means amide [-CONH2]<\/p>

- Modifications on the side chain of amino acids are depicted in the parenthesis after the corresponding amino acid. For example; phosphorylated serine = S(PO3H2) or epsilon-N-acetylated lysine = K(Ac)<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n What is a peptide counterion?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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\u5728\u80bd\u751f\u4ea7\u8fc7\u7a0b\u4e2d\uff0c\u5408\u6210\u548c\u7eaf\u5316\u6eb6\u6db2\u4e2d\u7684\u79bb\u5b50\u4f1a\u4e0e\u80bd\u5e26\u7535\u7684\u6c28\u57fa\u9178\u4fa7\u94fe\u7ed3\u5408\uff0c\u5f62\u6210\u76d0\u3002\u8fd9\u4e9b\u79bb\u5b50\u88ab\u79f0\u4e3a\u80bd\u53cd\u79bb\u5b50\uff0c\u6709\u52a9\u4e8e\u5e73\u8861\u80bd\u7684\u7535\u8377\u3002<\/span><\/span><\/p>

\u4e09\u6c1f\u4e59\u9178\uff08TFA\uff09\u5e38\u7528\u4e8e\u80bd\u7684\u5408\u6210\u548c\u7eaf\u5316\u3002<\/span><\/span><\/p>

\u5b83\u4e0e\u78b1\u6027\u6c28\u57fa\u9178\uff08\u4f8b\u5982\u8d56\u6c28\u9178\u3001\u7cbe\u6c28\u9178\u3001\u7ec4\u6c28\u9178\uff09\u548c\u6e38\u79bb\u7684N\u7aef\u80fa\u5f62\u6210\u4e09\u6c1f\u4e59\u9178\u76d0\u3002\u56e0\u6b64\uff0c\u4e09\u6c1f\u4e59\u9178\u76d0\u5f80\u5f80\u662f\u9ed8\u8ba4\u7684\u53cd\u79bb\u5b50\u3002<\/span><\/span><\/p>

\u4e0e\u80bd\u7ed3\u5408\u7684TFA\u5206\u5b50\u7684\u6700\u5c0f\u6570\u91cf\u4e0e\u7ed9\u5b9a\u80bd\u5e8f\u5217\u4e2d\u78b1\u6027\u6b8b\u57fa\u7684\u6570\u91cf\u6210\u6b63\u6bd4\u3002\u56e0\u6b64\uff0c\u80bd\u4e2d\u5b58\u5728\u7684\u78b1\u6027\u6b8b\u57fa\u6570\u91cf\u8d8a\u591a\uff0c\u51bb\u5e72\u7c89\u7684\u51c0\u80bd\u542b\u91cf\u5c31\u8d8a\u4f4e\u3002\u4e3a\u4e86\u5c06\u6837\u54c1\u4e2d\u5b58\u5728\u7684TFA\u6216\u6c34\u7684\u542b\u91cf\u8003\u8651\u5728\u5185\uff0c\u6211\u4eec\u5efa\u8bae\u5bf9\u6bcf\u4e2a\u5b9a\u5236\u80bd\u90fd\u8fdb\u884c\u80bd\u542b\u91cf\u6d4b\u5b9a\u3002<\/span><\/span><\/p>

\u6c34\u548c\u4e09\u6c1f\u4e59\u9178 (TFA) \u662f\u7eaf\u5316\u8fc7\u7a0b\u4e2d\u7684\u526f\u4ea7\u7269\u3002\u7136\u800c\uff0cTFA \u53ef\u80fd\u4f1a\u5bf9\u00a0<\/span><\/span>\u4f53\u5185<\/span><\/span><\/i>\u548c\u4e34\u5e8a\u524d\u7814\u7a76\u9020\u6210\u6bd2\u6027\u62c5\u5fe7\u3002\u56e0\u6b64\uff0cMOL Changes \u63d0\u4f9b\u65e0\u6bd2\u7684\u918b\u9178\u76d0\u3001\u6c2f\u5316\u7269\u6216\u94f5\u76d0\u4ea4\u6362\u5242\u3002<\/span><\/span><\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n \n

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\n \n \n hy are peptides containing Cys, Met, or Trp difficult to synthesize?<\/span>\n\n \n
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\n \n\t\t\t\t\t\t\t\t\t\t<\/i> <\/div>\n\n
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Peptides containing Cys, Met, or Trp are challenging to synthesize and obtain high-purity products. This is mainly due to the instability and susceptibility to oxidation of these functional groups. Special attention is required for the use and storage of these peptides to avoid repeated opening of the vials.<\/p> <\/div>\n\n <\/div>\n\n <\/div>\n\n <\/div>\n <\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Did we miss your question? Drop us a line<\/a> and we will
get back within 24 hours.<\/p>\n\t\t\t\t<\/div>\n\t\t\t<\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

Frequently Asked Questions Simply to Complex from Milligrams to Kilograms Custom Quote Request How to store peptides? Lyophilized Peptides For long-term storage of peptides, we recommend storing them as a solid powder. Lyophilized peptides can be stored at -20\u00b0C or lower with minimal degradation. Customers are advised to re-inspect customized peptides every 2 years from […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"elementor_header_footer","meta":{"footnotes":""},"class_list":["post-1015","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/pages\/1015","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/comments?post=1015"}],"version-history":[{"count":0,"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/pages\/1015\/revisions"}],"wp:attachment":[{"href":"https:\/\/molchanges.com\/zh\/wp-json\/wp\/v2\/media?parent=1015"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}