Protein in tissues

Metallothioneins are a group of small proteins (about 6.5 kDa), found in the cytosol of cells, particularly of liver, kidney, and intestine. They have a high content of cysteine and can bind copper, zinc, cadmium, and mercury. The SH groups of cysteine are involved in binding the metals. Acute intake (eg, by injection) of copper and of certain other metals increases the amount (induction) of these proteins in tissues, as does administration of certain hormones or cytokines. These proteins may function to store the above metals in a nontoxic form and are involved in their overall metaboHsm in the body. Sequestration of copper also diminishes the amount of this metal available to generate free radicals. 

Amyloidosis Occurs by the Deposition of Fragments of Various Plasma Proteins in Tissues... 

Maleszewski J, Lu J, Fox-Talbot K, et al. Robust immunohistochemical staining of several classes of proteins in tissues subjected to autolysis. J. Histochem. Cytochem. 2007 55 597-606. 

Formaldehyde fixes proteins in tissue by reacting with basic amino acids— such as lysine,5 7—to form methylol adducts. These adducts can form crosslinks through Schiff base formation. Both intra- and intermolecular cross-links are formed,8 which may destroy enzymatic activity and often immunoreactiv-ity. These formaldehyde-induced modifications reduce protein extraction efficiency and may also lead to the misidentification of proteins during proteomic analysis. 

Dyer, S.D., G.L. Brooks, K.L. Dickson, B.M. Sanders, and E.G. Zimmerman. 1993. Synthesis and accumulation of stress proteins in tissues of arsenite-exposed fathead minnows (Pimephales promelas). Environ. Toxicol. Chem. 12 913-924. 

Strong acid, strong oxidizer, corrodes metals, reacts with protein in tissue Strong acid, corrodes metals, HCl gas damages respiratory tract Corrodes metals, dissolves glass, causes bad burns... 

Proteins can be detected in tissue sections or cell cultures using similar immune detection systems. Use of an antibody to detect specific proteins in tissues is called immunohistochemistry, whereas detection of proteins in cell suspensions is called immunocyto-chemistry. Tissues can be prepared by fixation and embedding in paraffin wax, or by rapid freezing in a compound that inhibits ice formation in the tissue, so as to preserve cell morphology. Some antibodies do not work well with paraffin-embedded tissues, probably because the antibody cannot access the antigen properly (133). The most common labeling system used for detection of the bound antibody is an enzyme-coupled secondary antibody that produces a color reaction... 

Enzyme-linked immunosorption assay can be used to measure HER-2 protein in tissue homogenates or in serum. It is a relatively simple technique and is well suited to automation (van de Vijver, 2001). However, when tumor cytosolic fractions are used, histological information is lost and invites the undesirable dilution effect. Therefore, the ELISA assay is not used routinely to determine HER-2 status. 

Chaurand, P., Schwartz, J., and Caprioli, R. M. (2004). Profiling and imaging proteins in tissue sections by MS. Anal. Chem. 76 87A-93A. 

Protein Determinations The biuret assay (23) was employed for determining protein in tissue samples. 

Stowers, S.J., and Anderson, M.W. Ubiquitous binding of benzo(a)pyrene metabolites to DNA and protein in tissues of the mouse and rabbit. Chem. Biol. Interact. 51 151-166, 1984. 

Current evidence strongly supports the presence of two classes of binding between lipids and proteins in tissues. The first, which represents nearly 98%... 

Reverse transcription-polymerase chain reaction (RT-PCR), northern and western blotting, and immunoassays have been used for detection of kallerin mRNA and protein in tissue extracts of ovarian, breast, testicular, and prostate tumors. Immunohistochemical techniques have been used for the detection of KLK7 in ovarian tumors and KLKIO in ovarian and testicular tumors. The serum levels of KLK3 (PSA) and KLKll are evaluated by immunoassay. 

Palfrreyman, J. W., Thomas, D. G. T., and Ratcliffe, J. G., Radioimmunoassay of human myelin basic protein in tissue extracts, cerebrospinal fluid and serum and its clinical application to patients with head injury, Chin. Chim. Acta, 82, 259, 1978. 

While many proteins in tissues may thus easily form copper complexes, there are a few proteins of which copper is an integral part. Copper in these proteins is part of the molecular structure and not in dissociation equilibrium with ionic copper in the solution there is a characteristic ratio between moles of protein and atoms of associated copper. These and a few other criteria, discussed in detail by Vallee (V3), make these proteins a special class of metal-protein complexes and establish them as metalloproteins. 

Finally, ITP has been applied to the investigation of proteins in tissues and membranes, e.g., brain tissue (LI, Z2), eye lens (B17-BI9), and cell membranes (B14), and, although these uses are not relevant to clinical chemistry today, they do reflect the potential of the technique. 

Alternatively, imaging mass spectrometry (IMS) using matrix-assisted laser des-orption/ionization (MALDI) can be used to simultaneously map the distribution of pharmaceuticals in thin tissue sections to determine how a drug is distributed in animal tissues [6-9], MALDI-IMS has been extensively employed to measure macromolecules such as peptides and proteins in tissue sections [10-13] (Figure 11.1). Although MALDI-IMS has been applied almost exclusively as an analytical tool for... 

Reyzer, M.L. and Caprioli, R.M., MALDI-MS-based imaging of small molecules and proteins in tissues, Curr. Opin. Chem. Biol., 11, 29, 2007. 

As was first described in 1997 [4], the application of MALDI MS to the direct analysis of proteins in tissue sections is illustrated in Figure 12.1. The general procedure is to obtain a thin section of a sample of interest, apply matrix (which is necessary for the MALDI process), and then acquire mass spectra at discrete x-, y-coordinates over the entire sample section. Each individual mass spectrum contains signals corresponding to proteins (and other endogenous compounds, including peptides, lipids, and metabolites) present in the sample at a unique set of coordinates. The intensities of any given molecular species may then be plotted as a function of position on the sample surface. 

Insulin is the major anabolic hormone. It promotes the storage of nutrients as glycogen in liver and muscle, and as triacylglycerols in adipose tissue. It also stimulates the synthesis of proteins in tissues such as muscle. At the same time, insulin acts to inhibit fuel mobilization. 

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