Ideal protein marker

Measurements of the levels of semm proteins such as albumin, transthyretin (also known as prealbumin), transferrin and retinol-binding protein are used as biochemical parameters in the assessment of protein energy malnutrition (Table 17-1). An ideal protein marker should have rapid turnover and present in sufficiently high concentrations in semm to be measured accurately. Transthyretin has these properties it is a sensitive indicator of protein deficiency and is effective in assessing improvement with refeeding. 

The selection of a suitable molecular target is an essential step in the design of any ligand-based therapeutic. Tumor-associated markers are usually proteins or carbohydrates that are abnormally expressed or overexpressed in the tumor environment. Fundamental prerequisites of an ideal tumor-associated marker are specificity, abundance and stability, together with good accessibility for ligand molecules... 

Distorted bands are the result of bad sample appbcation, adsorption of protein to the column material, or a balance of protein between different polymerization states. A prebminary run with BSA and/or adding TRITON-X-100 or salt to the column buffer helps against the adsorption to the column material. Ideally, you apply colored markers (e.g., a mixture of cytochrome c, dextran blue, potassium dichromate) to the column before the run to check for run properties and band distortion. 

The GFR can be estimated by clearance measurements of endogenous or exogenous small molecules (urea, creatinine, 2-MPT, inulin, cystatin C, iohexol, or iodixanol). An ideal marker of GFR should be primarily excreted by the kidneys, freely filtered by the glomerulus, and neither secreted nor reabsorbed by the tubule. It should also be supplied to the plasma at a constant rate and exhibit no or minimal protein binding. If these criteria are met, such as for inulin, the GFR is equivalent to the renal/urinary clearance of the substance, as defined earlier in this chapter. 

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