We completed a study to show that DNA is completely destroyed at pH 2, and demonstrated that our collagen products do not contain DNA.

The collagen is fully hydrolyzed. The amino acid analysis is done using the Waters AccQ-Tag derivatization method.During the acid hydrolysis step, asparagine (N) is converted to aspartic acid (D) and glutamine (Q) is converted to glutamic acid (E). Tryptophan (W), if present, is destroyed during acid hydrolysis. Experimentally, one can determine the picomoles (pmol) of each amino acid per injected detected using amino acid standards.For the concentration determination, the total number of pmol of each amino acid is summed to get the total pmol of the 18 amino acids detected. The total pmol amino acids is divided by the theoretical number of amino acid residues in collagen based on the published sequence. The result is the pmol of collagen injected. The result is then multiplied by the dilution and 300,000 is used as the collagen molecular weight to get to mg/mL. The molecular weight of collagen is not well agreed upon.

Diluting with 1X PBS (rather than water or 0.01 N HCl) would have an effect for coating purposes. It would change the pH of the diluted collagen solution from acid to neutral pH. The pH change will transform the collagen molecules from a molecular form to a fibrillar form; and then the nature of coating surface will be changed from a monomeric coating to a fibrillar coating.

We use thefollowing antibodies from SouthernBiotech:

1. 1310-02 – Goat Anti-Type I Collagen-FITC

2. 1310-08 – Goat Anti-Type I Collagen-BIOT

3. 7100-05 – Streptavidin-HRP

The major collagen molecular species in our Type I collagen products are monomers (approx. 70%), but there are dimers, trimers and a few percentages of oligomers too (approx. 30%) with some minor amounts of collagen fragments. The collagen monomer is a rod shaped molecule with 300 nm in length and 1.5 nm in diameter. The dimer, trimer and oligomer are 600 nm, 900nm and even longer in length respectively. According to the coating procedures, the collagen molecules are attached to the charged polystyrene surface randomly by charge or affinity in acid conditions during the 1-2 hrs incubation period at 37°C, and any unattached materials are removed by aspiration and rinsing. Therefore, the coated surface is a single layer of collagen monomer, dimer, trimer and oligomer mixtures.The thickness of the mono-molecular layer is dependent on how those molecules are attached on the surface. The coating density thickness would generally be characterized as a 1 molecule thickness which could be ranging from a few nanometers to a few hundred nanometers with the whole surface being covered by collagen.

The net charge of Type I collagen products’ (PureCol^®, Bovine Collagen and VitroCol®, Human Collagen) molecule is directly related to the pH. At an acidic pH, the amino acids (zwitterions) along the collagen molecule are positively charged, making the entire collagen molecule positive. At the isoelectric point (or zone) of collagen, around pH 7-8, the amino acids along the collagen molecule are positively and negatively charged, making the net charge of the collagen molecule close to zero. At a basic pH, the amino acids along the collagen molecule were negatively charged, making the entire collagen molecule negative.

Further, the nature of the charge of the collagen coating surface will be dependent on the type of coating applied. For a monomeric collagen coatings when the collagen is applied under an acidic pH condition, the surface is positively charged. If the surface is rinsed with pH neutral buffer or media then it will change the charge of the collagen surface net charge close to zero. For a 3D gel coating, the collagen prepared under neutral pH; the net charge of the collagen surface is close to zero.

Using rotary shadowing technique under transmission electron microscopy, it was found that our collagen, on average, consists of approximately 80% monomers, 13% dimers, trimers, and oligomers with the remaining 7% collagen fragments.

Yes.The collagen molecule in PureCol, Nutragen, VitroCol, and all of our other Atelo collagen products were prepared from native collagen matrix by pepsin treatment under controlled conditions to remove the non-helical portion, telo-peptides, only and the helical portion is intact. In this case, the enzymatic active sites for MMP (Matrix Metalloproteinase), such as for Mammalian Collagenase Matrix Metalloproteinase 8 (MMP-8), on the molecule was preserved.

These pepsin treated collagen products should behave as native intact collagen.

TGF beta would have been digested with the pepsin enzymatic digestion step. It was undetectable by SDS PAGE silver stain as well. We didn’t do any specific measurements by ELISA however but presences of TGF betais not anticipated.

We primarily use the Biuret method, but we also use BCA, AAA, and hydroxyl-proline assays.

- Collagen solutions that are frozen tend to have issues forming 3D hydrogels, and will likely not work. The solutions should still be good for 2D coatings.

- Collagen solutions that are left out at room temperature for extended periods of time may show signs of degradation, which will affect the formation of 3D hydrogels. It is likely still fine for 2D coatings.

Our recommendation is this: If you are using the product directly for a publication, we highly suggest buying a new bottle if the one you have was compromised.