CJC-1295 with and without DAC: two different materials

Two products, one name, three letters between them

CJC-1295 is listed two ways across this category: with DAC and without DAC. The three letters are doing a great deal of work. They do not describe a grade, a concentration, or a supplier preference — they describe a chemical difference in the molecule itself, and the two materials have different masses, different chromatographic behaviour, and different documentation.

DAC stands for Drug Affinity Complex. In the material sold under that name, the peptide carries an additional chemical group attached to it — a maleimide-bearing linker designed, in the published work, to form a covalent bond with a carrier protein once it is in a biological system. The material sold without DAC is the peptide chain alone, and is frequently listed under its other name, modified GRF (1-29).

A vial of one is not a substitute for a vial of the other, and the product title is not what tells you which you have.

What each one is

Both are analogues of the first 29 residues of growth-hormone-releasing hormone, carrying substitutions at positions in the native sequence that are, in the published chemistry, the points most vulnerable to enzymatic breakdown. The substitutions are the reason the material is described as modified rather than native.

Treat the masses above as orientation. The certificate for the lot in hand is the authoritative record, and where a report disagrees with this page, the report governs.

How a report tells them apart

The mass difference between the two is roughly 290 units — small relative to the molecules themselves, but far larger than any method's tolerance, so a mass-based identity result separates them without ambiguity. A result near 3,360 describes the chain alone; a result near 3,650 describes the linker-bearing material.

Where identity is reported by retention-time matching instead — written as HPLC-RTM on a certificate — the reference standard is what defines the answer, so the report needs to name which material the standard was. The linker is hydrophobic, which means the DAC-bearing material is retained longer on a reversed-phase column than the plain chain under the same method. Two materials that elute at visibly different times are not hard to distinguish once you know which one the method was set up for.

What to look for on the chromatogram

• A 29-residue chain is a long synthesis. Every coupling step is another chance for a deletion sequence, and deletion products of a long chain elute close to the parent. Peaks immediately adjacent to the main peak are the expected signature here, and their combined size is more informative than the headline percentage on its own.
• For the DAC material, incomplete conjugation is the characteristic impurity. Material that did not receive the linker is chemically the no-DAC peptide — which means an impurity peak in a DAC lot may be a perfectly good molecule that simply is not the one on the label. This is a case where a high purity figure and a correct identity result still leave a question the chromatogram answers.
• Areas should account for the whole run. If the integrated percentages do not total 100, the report should state what was excluded and why.

How to read an HPLC chromatogram covers the plot itself; what a purity percentage means covers how the figure is derived.

Storage of the lyophilized solid

Both materials are supplied as freeze-dried solids and both are governed by the same two conditions: temperature and moisture. Cold storage slows every chemical process available to the molecule, and the solid is hygroscopic, so a vial opened before it has equilibrated to room temperature will draw water out of the air.

The DAC material has one additional consideration. The maleimide group that defines it is a reactive handle by design — that reactivity is the point of the molecule — and reactive groups are, as a class, less forgiving of moisture and warmth over long periods than an unmodified chain. Stability is a documented property rather than an assumed one; where a retest date is stated, the question worth asking is what data supports it. See storing lyophilized research materials.

Scope of this documentation

This page concerns material identification and analytical documentation for laboratory research. It does not recommend personal, human, clinical, therapeutic or veterinary applications. Published research findings do not establish the properties of Arctic stock; use the applicable lot record and its stated methods and limitations.

Related documentation