Electrophoresis is the process of moving charged molecules in solution by applying an electrical field across the mixture.

Technique invented by Tiselius in 1937,Nobel prize in 1948.

Molecules moved with a speed dependent on their charge, shape, and size.

Electrophoresis is used:

for analysis and purification of very large molecules

(proteins-serum, CSF, urine, haemoglobin, iso enzymes,

lipoproteins, nucleic acids – DNA, RNA)

for analysis of simpler charged molecules (peptides,

nucleotides, and simpler ions).

The electrophorosis unit

1. Vertical gel system

2. Horizontal gel system

Power supply

1. Current

2. Power

3. voltage

Positive ions move towards cathode Negative ions move towards anode

Electrophoretic mobility :rate of migration (cm/sec) per unit field strength (v/cm)

μ = Q/6 π r ɳ

μ = elctrophoretic mobility in cms

Q = net charge on ion

r = ionic radius of solute

ɳ = viscosity of buffer solution in which migration is occurring

Factors influencing electrophoretic mobility: Net charge of the molecule Size and shape Concentration of the molecule in solution Electrical field strength according to ohms law V=IR where V = voltage , I = current & R = resistance Temperature W = I R rise in temp. of electrophoresis medium

2

1. Increases rate of diffusion

2. Formation of convection currents – mixing of separated

sample.

3. Thermal instability leads to denaturising of proteins, loss of

enzyme activity

4. Decrease of viscosity of buffer

Time of electric field strength

Properties of supporting medium : pore size, adsorption effect.

pH of buffer

Wick flow

Endosmotic flow

The surface of the silicate glass capillary contains negatively-charged functional groups that attract positively-charged counterions. Positively-charged ions migrate towards the negative electrode and carry solvent molecules in the same direction. Overall solvent movement is called electroosmotic flow. During a separation, uncharged molecules move at the same velocity as the electroosmotic flow (with very little separation). Positively-charged ions move faster and negatively-charged ions move slower.

Carries applied current Establishes pH at which electrophoreses is performed

Determines the charge on the ionic solute

Ionic strength :μ = 0.5 Ʃ c zc = ionic concentration in mol/lz = charge on ion

2i i

Buffer ionic strength influences

1. Conductance of support

2. Thickness of ionic cloud

3. The rate of its migration

4. Sharpness of electrophoretic zones

Low pH buffers : phosphate ,acetate ,formate ,citrate

High pH buffers : barbitone ,tris , tricine , borate ,CAPS

Necessary to :1. Control convection / diffusion2. Apply sample3. Observe the result & to detect components

Ideal properties :1. No adsorption of sample2. No charge3. Controlled restriction of molecule movement

YES: uses molecular weight as criteriaNO: when molecular weight independent separation necessary

Zymography is an electrophoretic method based on SDS-PAGE.

Substrate for enzyme is copolymerized with polyacrylamide gel.

Following electrophoresis, gel is incubated in appropriatve buffer solution.

Gel is subsequently stained. Areas of digestion appear as clear bands

against a darkly stained background.

Proteins are separated in pH gradient. Protein migrate into the point where its net charge is zero – isoelectric

pH. Protein is positively charged in solutions at pH values below its pI. Protein is negatively charged in solution at pH above its pI

In the first dimension, proteins are resolved in according to their isoelectric points (pIs) using immobilized pH gradient electrophoresis (IPGE), isoelectric focusing (IEF), or non-equilibrium pH gradient electrophoresis.

In the second dimension, proteins are separated according to their approximate molecular weight using sodium dodecyl sulfate poly-acrylamide-gel-electrophoresis (SDS-PAGE).

Silver nitrateCSF proteinsSilver diamine

590 em254 exEthidium bromideDNA fragments

600Sudan black B520Oil red O

570Fat red 7BLipoprotein zones

570Nitrotetrazolium blueIso enzymes

520Ponceau S

560Coomassie brilliant blue R 250

595Coomassie brilliant blue G 250

640Amido black BSerum proteins

Nominal wave length

stainSeperationtype

Silver nitrateCSF proteinsSilver diamine

590 em254 exEthidium bromideDNA fragments

600Sudan black B520Oil red O

570Fat red 7BLipoprotein zones

570Nitrotetrazolium blueIso enzymes

520Ponceau S

560Coomassie brilliant blue R 250

595Coomassie brilliant blue G 250

640Amido black BSerum proteins

Nominal wave length

stainSeperationtype

Reliable quantification of stain zones is done by densitometry

1. light of appropriate wavelength2. Linear response from instrument3. Transparent background in strip being

scanned

Used as an electric field to separate the protein in blood serum into groups of similar size, shape and charge.

pH 8.6 Used to determine whether the hormonal immunity function normally or not

ALBUMIN GLOBULIN

ALPHA (α) BETA (β) GAMMA(γ)

The largest protein component of human serum It functions:

To keep the blood from leaking out of blood vessel Carry some medicine & other substances

Moving toward the negative portion of the gel Involve of α1 & α2 components

• α1 is comprised of : α1-antitrypsin Thyroid binding globulin Trancortin

- HDL also include in this fraction

• α2 consist of: Ceruloplasmin α2-macroglobulin Haptoglobin- binds to hemoglobin

Beta1- Composed mostly of transferrin

Beta2- Contains β-lipoprotein- IgA, IgM & sometimes IgG along

with complement also can be identified in this fraction

Has 2 peaks: β1 β2

Function:

Help carry substances, e.g: iron Fight infection

Most of clinical interest focused in this fraction

Contains immunoglobulin (antibodies)

Function:Help prevent & fight infection

Albumin 1 2

+ -

Albumin 1 2

Albumin 1 2

+ -

Albumin 1 2

+ -

“- bridging”

Albumin 1 2

+ -

Albumin 1 2

+ -

However, in a particular disorder, the serum electrophoretic will show normal pattern.

Therefore, in these cases, we need to use the CSF or urine instead of serum.

Detection of Bence Jones Protein in Urine Detection of oligoclonal

band in CSF

Primary lipoproteinemia (Frederickson classification)

Type I -hyperchylomincronemia

Type II – hyperbetalipoproteinnemia

Type III – ‘broad beta’ abnormal lipoproteinemia

Type IV – carbohydrate induced & endogenous hypertriglyceridemia

Type V – mixed triglyceridemia (carbohydrate & fat induced

High and low values Higher-than-normal amounts of both hemoglobin A2 and hemoglobin F may mean a mild form of thalassemia is present. A very low level of hemoglobin A and a high level of hemoglobin F may mean a more severe form of thalassemia. High levels of hemoglobin F may be seen in a rare condition called hereditary persistence of fetal hemoglobin. Hemoglobin S in moderate amounts can mean that sickle cell trait is present. Hemoglobin S in high amounts means sickle cell disease. Hemoglobin C in low amounts can mean that hemoglobin C trait is present. Hemoglobin C in high amounts means hemoglobin C disease, which causes anemia and an enlarged spleen. Hemoglobin types S and C mean hemoglobin S-C disease, which causes a mild or moderate form of sickle cell disease. Hemoglobin E in low amounts means the presence of hemoglobin E trait. Hemoglobin E in high amounts means hemoglobin E disease, which causes anemia and smaller-than-normal red blood cells. Hemoglobin types other than S, C, D, and E are rare. But over 400 types of abnormal hemoglobin have been found.

Capillaries are typically of 50 µm inner diameter and 0.5 to 1 m in length. Due to electroosmotic flow, all sample components migrate towards the negative electrode.

The capillary can also be filled with a gel, which eliminates the electroosmotic flow. Separation is accomplished as in conventional gel electrophoresis but the capillary allows higher resolution, greater sensitivity, and on-line detection.