Dear Damodar,

you can use dialysis bag with molecular weight cut off 6-8 kDa for purifying collagen type 1.

Type I collagen chains (the monomers seen in SDS gel electrophoresis) have an apparent molecular mass of over 100,000 Daltons.  Triple helical collagen (tropocollagen) would be three times larger.  Just about any kind of dialysis tubing should work if the goal is removal of low molecular weight salts and other small impurities.

Can i use the dialysis tubing having the following specification, as i am going to order from the vender soon:

Packaged: wet

Preservative: 0.05%Sodium Azide

Disc/Flat Sheet: NO

MWCO Dalton: 8K

Flat Width: 40mm

Diameter: 25.5mm

Vol/Length: 5.1

P.S. Any proper specification if you have that you order previously can be fruitful for me.

Or, can i go for this specification:

Packaged: Dry

Preservative: Glycerin

Disc/Flat sheet: Yes

MWCO Daltons: 6000-8000

Trial size: 5 meter

Flat Width: 40mm

Diameter: 25.5mm

Vol/Length: 5.1

You can use a dialysis bag with a molecular weight cut off 12-25 kDa for purifying collagen type 1.