Lecture 2 -- Plasma Proteins

oligopeptides

polymers of amino acids that have up to 20 peptides

polypeptides

polymer of amino acids with more than 20 peptides

Examples of fibrous (structural) proteins

• fibrinogen

• troponin

• collagen

• myosin

Examples of globular proteins

• hemoglobin

• enzymes

• peptide hormones

• plasma proteins (including albumin)

Are globular proteins compact

yes

What does it mean when globular proteins are compact

• little or no space for water in interior of molecule where most of the hydrophobic R groups are located

• most polar R groups are on surface of protein

Having polar R groups on the surface of the protein will influence __

• protein solubility

• acid-base behavior

• electrophoretic mobility

What 2 things can cause proteins to denature? What does denaturation result in?

• high temps and extreme pH

• proteins lose solubilities and biological activities

• many enzymes lose catalytic activities after denaturation

5 properties of proteins that can be used to separate, identify, and assay proteins

1. molecular size

2. differential solubility

3. electrical charge

4. adsorption on finely divided inert materials

5. specific binding to antibodies, coenzymes, or hormone receptors

4 methods to separate proteins from smaller molecules based on molecular size

1. dialysis

2. ultrafiltration

3. gel filtration chromatography

4. density gradient ultracentrifugation (ex: used to pull lipoproteins/lips from lipemic specimens)

4 things that affect protein solubility

1. pH

2. ionic strength

3. temperature

4. dielectric constant of the solvent

How does varying ionic strength affect protein solubility

• more soluble = salting in

• less soluble = salting out

Albumin is soluble in __

water and 50% ammonium sulfate

albumin is insoluble in __

saturated ammonium sulfate

Fibrinogen and gamma globulins are generally insoluble in __

water

hemoglobin is insoluble but myoglobin is soluble in __

60% ammonium sulfate

pH impacts electrical charge by introducing, enhancing, or changing __

surface charges that migrate at different rates in an electrical field

8 possible protein functions

• maintain osmotic pressure of plasma

• bind + transport hormones, vitamins, metals, drugs, bilirubin within the blood (reservoirs for release and use)

• enzymes (catalyze essential biochem rxns)

• regulate metabolism (protein, polypeptides, oligopeptide hormones)

• protect against infection (antibodies and complement)

• solubilize lipids (apolipoproteins)

• carry oxygen (hemoglobin)

• affect hemostasis (coagulation factors)

Most plasma proteins are synthesized in __ and move to bloodstream through __

• the liver

• hepatic sinusoids and central liver veins

acute phase reaction

nonspecific response to inflammation or tissue damage

Acute phase reactants (APR)

proteins affected by the acute phase reaction

Positive APR

proteins whose levels rise during inflammation

7 examples of positive APRs

1. alpha 1 antitrypsin

2. alpha 1 acid glycoprotein

3. haptoglobin

4. ceruloplasmin

5. C3

6. C4

7. C-reactive protein (CRP)

Negative APR

proteins whose levels decrease in inflammation

3 examples of negative APRs

1. albumin

2. transferrin (normal to low in ACD)

3. transthyretin (prealbumin)

Acute phase reactant changes are triggered by __

cytokines release at site of injury

Plasma concentrations change at different rates after initial injury which means it can help us __

diagnose and monitor progress of inflammation or response to treatment

Transthyretin (TTR) is also known as __

prealbumin