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Enzyme Reagents
Human Albumin
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Gene ID: ALB
CAS#: 70024-90-7
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Methods of Preparation:
Sigma-Aldrich produces human serum albumin using a cold alcohol fractionation process derived from the traditional Cohn1,3 method as well as heat shock methods.2,4
Molecular Weight:
66,437 Da8 (based on amino acid composition). Commercial preparations contain varying degrees of post-translational modifications and genetic variants with molecular weight components mainly in the range of 66,437 to 66,600 Da
Deconvoluted mass spectrum of intact Native HSA
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Methods of Preparation:
Sigma-Aldrich produces human serum albumin using a cold alcohol fractionation process derived from the traditional Cohn1,3 method as well heat shock methods.2,4
Molecular Weight:
66,437 Da 8 (based on amino acid composition). Commercial preparations contain varying degrees of post-translational modifications and genetic variants with molecular weight components mainly in the range of 66,437 to 66,600 Da
Deconvoluted mass spectrum of intact Native HSA
Structure:5
Human albumin is a single peptide chain with one free sulfhydryl group on residue # 34 and 17 intrachain disulfide bonds.
Mass Spec Analysis of various commercial preparations indicates the presence of several post-translational modifications. Native human serum albumin is not a glycoprotein in the traditional sense. However, several genetic variants exist that may undergo enzymatic N-& O-glycosylation. Upon circulation in plasma, albumin often becomes glucosylated on ε amine groups of lysine and possibly arginine residues. This is the result of the non-enzymatic spontaneous Maillard Reaction between the carbonyl group of the open ring form of glucose, present in small amounts in plasma, forming a Schiff base with the exposed primary amines of circulating proteins such as albumin, insulin and hemoglobin. Sigma has also observed various degrees of glucosylation in recombinant preparations. Cysteinylation is also present in native and recombinant preparations.
Amino Acid Composition
| Amino Acid |
Asp |
Asn |
Thr |
Ser |
Glu |
Gln |
Pro |
Gly |
Ala |
Cys |
Val |
Met |
Ile |
Leu |
Tyr |
Phe |
His |
Lys |
Trp |
Arg |
| Residues |
39 |
15 |
30 |
22 |
60 |
23 |
25 |
12 |
63 |
35 |
39 |
6 |
8 |
61 |
18 |
30 |
16 |
58 |
1 |
23 |
Fatty Acid Composition of Human Albumin.Circulating plasma albumin typically contains 0.5-1.5 moles of fatty acid bound to one mole of albumin. Upper ranges of 4-9 moles per mole have been reported. 9,10 Alternatively, Sigma offers fatty acid depleted native human albumins.
| Saturated Fatty Acids |
Native .HSA |
rHSA expressed in Rice |
| Lauric |
12:0 |
<1% |
0.2% |
| 13:0 |
<1% |
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| Myristic |
14:0 |
1.50% |
1.5% |
| Pentadecenoic |
15:0 |
< 1% |
0.1% |
| Palmitic |
16:0 |
24.70% |
12.5% |
| 17:0 |
<1% |
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| Stearic |
18:0 |
1.50% |
0.5% |
| Arachidic |
20:0 |
<1% |
0.0% |
| Bohenic |
22:0 |
Not Tested |
0.0% |
| Lignoceric |
24:0 |
Not Tested |
0.0% |
| Monosaturated Fatty Acids |
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| Myristoleic |
14:1 |
<1% |
0.0% |
| Palmitoleic |
16:1w7 |
<3.1% |
0.8% |
| Oleic |
18:1w9 |
<33.1% |
35.9% |
| 18:1w7 |
<1% |
0.0% |
| 24:1 |
<1% |
0.0% |
| Diunsaturated Fatty Acids |
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| Linoleic |
18:2w6 |
<20.0% |
44.8% |
| Polyunsaturated Fatty Acids |
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| α-Linolenic |
18:3w3 |
<1% |
3.6% |
| 18:3w6 |
<1% |
0.0% |
| 20:1w9 |
<1% |
0.0% |
| 20:1w9 |
<1% |
0.0% |
| 20:2w6 |
<1% |
0.0% |
| 20:3 |
1.40% |
0.0% |
| Arachidonic |
20:4 |
5.00% |
0.0% |
| 20:5 |
<1% |
0.0% |
| 22:1w9 |
<1% |
0.0% |
| 22:4w6 |
<1% |
0.0% |
| 22:5w6 |
<1% |
0.0% |
| 22:5w3 |
<1% |
0.0% |
| 22:6w3 |
<1% |
0.0% |
Physical Properties5
| Sedimentation constant, S20,W X 1013 |
4.6 (monomer), 6.5 (dimer) |
| Diffusion constant, D20,W X 107 |
6.1 |
| Partial specific volume, V20 |
0.733 |
| Intrinsic viscosity, η |
0.042 |
| Frictional ratio, f/f0 |
1.28 |
| Overall dimensions, Å |
38 X 150 |
| Isoelectric point (Γ/2 = 0.15) |
4.7 |
| Isoionic point (Γ/2 = 0) |
5.2 |
| Electrophoretic mobility, pH 8.6, G/2 = 0.15 |
-5.9 |
| Refractive index increment (578 nm) X 10-3 |
1.89 |
| Optical absorbance, A279 nm (1 gram/liter) |
0.531 |
| Mean residue rotation, [m']233 |
8590 |
| Mean residue ellipticity |
17 [q]209 nm; 16 [q]222 nm |
| Estimated α-helix, % |
48 |
| Estimated β-form, % |
15 |
Applications and Other Properties7
Due to its high charge to mass ratio, albumin binds water, Ca2+, Na+, K+, fatty acids, bilirubin, hormones and many xenobiotic drugs. The main biological function of albumin is to regulate the colloidal osmotic pressure of blood. Human and bovine albumins contain 16% nitrogen and are often used as standards in protein calibration studies. Due to their free hydrophobic region, fatty acid free albumins are used to solubilize lipids in tissue culture, and are also used as blocking agents in Western blots or ELISA applications. Globulin free albumins are suitable for use in applications where no other proteins should be present (e.g., electrophoresis).
Powders: Native Preparations
Powders: Recombinant Preparations
Solutions: Native Preparations
Solutions: Recombinant Preparations
Protein Standards
Modified HSAs
References
- E.J. Cohn, J. Amer. Chem. Soc., 68, 459 (1946).
- R.F. Chen, J. Biol. Chem., 242, 173 (1967).
- E.J. Cohn, J. Amer. Chem. Soc., 69, 1753 (1947).
- Globulins are precipitated in a heat step following addition of caprylate, then removed by filtration.
- The Plasma Proteins, 2nd Ed., Vol. I, F. W. Putnam, Ed., pp. 133-181, Academic Press, New York (1975).
- S.C. Gill and P.H. von Hippel, Anal. Biochem., 182, 319 (1989).
- T. Scott and M. Eagleson, Concise Encyclopedia: Biochemistry, 2nd Ed., pp. 19-20, Walter de Gruyter, New York (1988).
- Sigma calculation based on sequence given by B. Meloun, et. al., FEBS Letters, 58(1), 134 (1975).
- The free fatty acids bound to human serum albumin. Saifer, A., Goldman, L., J. Lipid Res., 2, 268-270 (1961)
- Fatty acid enhancement of human serum albuminbinding properties. J. Biol. Chem., 252, 4043-4048 (1977)
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