Separating a protein by its charge, and what the deamidated bands mean

Published 26 October 2026 · REVIVE LAB UAE Research Desk · 5 min read
Somatropin has an isoelectric point of about 5.3. Deamidation converts a neutral asparagine side chain to an acidic one, so each event lowers the isoelectric point by a measurable step. Isoelectric focusing runs the protein through a pH gradient in which each variant stops where its net charge is zero, giving a ladder of bands: the main band and progressively more acidic variants. Capillary versions quantify the bands automatically. The method is specific to charge changes and therefore to deamidation, which the reversed-phase method sees only partly.

The principle

A protein placed in a stable pH gradient under an electric field migrates until it reaches the pH equal to its isoelectric point, where it carries no net charge and stops. Variants differing by one charge separate cleanly. The bands are stained or, in capillary format, detected by absorbance as they pass a window.

It is one of the oldest high-resolution protein methods and remains in pharmacopoeial use.

What the ladder shows

The main band is intact somatropin. The first acidic band is singly deamidated protein, mostly at asparagine 149 or 152; the next is doubly deamidated. Their relative intensities give the degree of deamidation, which rises with time in solution and is a direct measure of chemical age. Basic variants are rare for this protein.

The monograph sets a limit on the acidic variants as a group.

Together with the other methods

Reversed phase for oxidation and clips, size exclusion for aggregates, charge methods for deamidation, peptide mapping to locate any of them. A certificate carrying all four describes the lot fully; one carrying only purity by HPLC describes part of it.

Somatropin is supplied by REVIVE LAB UAE for laboratory research use only, with identity and purity documented for the batch. It is not for human or veterinary use, and no dosing, administration or protocol guidance is provided.

What it costs

FormatStrengthPriceAvailability
HGH Somatropin Pack24 mg (72 IU)AED 850In stock

Delivery is AED 40 flat and free on orders over AED 700. Payment is cash on delivery anywhere in the UAE, or USDT (TRC20) in advance, which takes 5% off the order total.

Frequently asked

The principle?

A protein placed in a stable pH gradient under an electric field migrates until it reaches the pH equal to its isoelectric point, where it carries no net charge and stops. Variants differing by one charge separate cleanly. The bands are stained or, in capillary format, detected by absorbance as they pass a window.

Does REVIVE LAB UAE provide dosing guidance?

No. REVIVE LAB UAE supplies research materials and provides no dosing, administration or protocol guidance of any kind. Every product is sold for laboratory research use only and is not for human or veterinary consumption.

How fast is delivery in the UAE?

Stock is held in Dubai. An order confirmed before 4 PM Dubai time is dispatched the same working day, reaching Dubai and Abu Dhabi the same day and the remaining emirates within 24 hours. Delivery is AED 40 flat and free over AED 700.

HGH Somatropin Pack — in stock, dispatched from Dubai
HPLC-verified, lot certificate on every carton, 24-hour delivery nationwide. Browse the catalogue → All peptides UAE

Related reading

Supplied for laboratory research use only. Not for human or veterinary consumption. REVIVE LAB UAE provides no dosing, administration or protocol guidance.