Zwitterion
Definition
A molecule carrying a positive and a negative charge at the same time while being neutral overall. Free amino acids exist as zwitterions at physiological pH, which is why they are far more water-soluble than their structures suggest.
What this means for research sourcing
Structure and identity terms are what a certificate of analysis is written in. Every Volta compound ships with its sequence, molecular weight and measured purity, so these terms map directly onto the specification on the product page.
Related Terms in Chemistry & Structure
Hydrophilic and Hydrophobic
Whether a region of a molecule associates with water or avoids it. The balance across a sequence sets solubility, how a peptide behaves on a reversed-phase column, and how readily it crosses a lipid membrane.
Solubility
How much of a peptide a given solvent will take into solution. It is sequence-specific rather than general: some materials need a trace of acid or a small percentage of organic solvent before water will carry them, and forcing the issue with agitation causes aggregation instead.
Denaturation
Loss of folded structure through heat, extreme pH or mechanical shear, without the backbone necessarily being cut. The mass can be unchanged while the activity is gone, which is why an identity test alone does not establish that a material is intact.
Counter-Ion
The small ion supplied alongside a charged peptide to balance it, usually acetate and sometimes trifluoroacetate. It is part of the powder's mass, so gross vial weight and peptide content are two different numbers.
Acetate Salt
The form most synthetic peptides are supplied in, with acetate as the counter-ion. Acetate is preferred over trifluoroacetate for work in cell culture, where residual TFA can be toxic at low concentrations.
TFA Salt (Trifluoroacetic Acid)
The counter-ion left behind by reversed-phase purification unless it is deliberately exchanged. Residual TFA affects cell-based assays and can be reported on a certificate, so a salt-form statement is worth reading rather than skipping.
Molar Ratio
In a blend, the proportion of one compound to another counted in molecules rather than in milligrams. Two blends with the same mass ratio have different molar ratios whenever the molecular weights differ, which they almost always do.
Nomenclature
The naming conventions a peptide arrives under. A single compound can carry a sequence-derived code, a developer's number, a trade name and an INCI name, and the suffixes carry information of their own: LR3 names a substitution, DAC names a linker, 176-191 names a residue span.