Biochemistry · Topic
Plasma proteins and electrophoresis !
Electrophoresis splits serum proteins into five bands; their shape helps recognise inflammation, cirrhosis, nephrotic syndrome or myeloma.
Updated 2026-11-01
Key facts
- On agarose at pH 8.6 proteins carry a negative charge and run to the anode. Order from the anode: albumin, α1, α2, β and γ.
- Albumin: the largest band (≈ 60 %). α1: α1-antitrypsin. α2: α2-macroglobulin, haptoglobin, caeruloplasmin. β: transferrin, LDL, C3. γ: immunoglobulins.
- M spike: a narrow, tall (monoclonal) band, almost always in γ; suggests a monoclonal gammopathy (MGUS, myeloma, macroglobulinaemia).
- Polyclonal increase (broad γ band): chronic inflammation, cirrhosis, HIV infection, autoimmune disease.
- Serum has no fibrinogen; plasma shows an extra band between β and γ.
In detail
- Normal total protein ≈ 6–8 g/dL; albumin ≈ 3.5–5 g/dL; the difference is the globulins.
- Acute inflammation: α1 and α2 rise (acute-phase proteins: α1-antitrypsin, haptoglobin, fibrinogen, CRP) and albumin falls (a negative acute-phase reactant).
- Cirrhosis: low albumin and a polyclonal γ rise with “β–γ bridging” (IgA fills the gap between the two bands).
- Nephrotic syndrome: albumin and IgG are lost in urine; α2 rises in proportion because the very large α2-macroglobulin is not filtered.
- α1-antitrypsin deficiency: a low or nearly absent α1 band.
- An M spike is confirmed by immunofixation (which heavy and light chain: IgG κ, IgA λ…) and by serum free light chains (κ/λ ratio).
- Prealbumin (transthyretin) is a faint band ahead of albumin; because it lasts about 2 days in blood, it reflects recent nutritional change.
- Also called
- Serum protein electrophoresis, SPEP, M spike
Clinical notes
- In an older adult with bone pain, anaemia, high calcium or kidney failure, electrophoresis with an M spike points to multiple myeloma.
- Hypoalbuminaemia causes oedema through low oncotic pressure and changes the measured total calcium (corrected for albumin).
- Low haptoglobin indicates haemolysis (it binds free haemoglobin and is cleared).
Related conditions
Related
- Albumin
- Immunoglobulins (antibodies)
- α1-antitrypsin
- Transthyretin (prealbumin)
- Amino acids: structure, charge and pKa
- Isoenzymes
- Hemoglobin variants (HbA, HbA2, HbF, HbS, HbC)
Test yourself
Think of the answer, then tap the question to see it.
Why is albumin the band that runs furthest towards the anode?
It has a low isoelectric point and a large negative charge at pH 8.6, and it is small compared with the globulins.
What does a narrow spike in the γ region indicate?
A monoclonal immunoglobulin made by a single plasma-cell clone: MGUS, myeloma or another gammopathy.
Which electrophoresis pattern is typical of cirrhosis?
Low albumin and a polyclonal γ rise with β–γ bridging from IgA.
Which band nearly disappears in α1-antitrypsin deficiency?
The α1 band, because α1-antitrypsin is its main component.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Protein electrophoresis - serum: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Immunoelectrophoresis – blood: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Total protein: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Free Light Chains: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.