细胞功能测定

Of all the organdies in rat hepatocytes, the nucleus is the largest and the most dense. It is therefore relatively easy to isolate in high purity and high yield. The majority of methods (1,2) involve the homogenization of the liver in isoosmotic sucrose followed by differential centrifugation and ...

Glycolipids are an important group of diverse molecules present in the plasma membrane and to a more limited extent in the intracellular membranes of the Golgi and lysosomal systems of eukaryotic cells. They are prominent as antigenic determinants and as the ligands for specific lectin bin ...

The function of many glycoproteins is directly related to the structure of their oligosaccharide chains (1–5). Subtle changes in oligosaccharide structure involving the linkage of or loss of single monosaccharide units are known to occur in many biological events. Knowledge of this fine ...

A strategy for determining the structure of a glycosaminoglycan (GAG) can be divided into three areas. The first is to establish its saccharide composition. This requires complete depolymerization of the parent chains to disaccharide products that can be purified, separated, and iden ...

The proteoglycans (PGs) are a large and varied family of complex macromolecules whose physical properties are dominated by their large sulfated polysaccharide chains (for a recent review, see ref. 1). They are widely distributed in the animal kingdom, but are not associated with any particu ...

Membrane enzymes may be peripheral or integral proteins. The attachment of peripheral enzymes is mediated mainly by association with other membrane proteins and consists primarily of hydrophilic, electrostatic interactions. Integral membrane proteins are primarily bound ...

The high resolution capacity of polyacrylamide gel electrophoresis (PAGE) (see Chapter 19) has resulted in the widespread application of this group of techniques to protein separations. PAGE procedures can provide characterization of proteins in terms of their charge, size, relat ...

As discussed in other chapters in this book (see especially Chapters 6, 7, 9, 23, and 24), many nucleases were first identified as such by their sequence identity to known nucleases. Several of these were isolated because they exhibited a seemingly unrelated activity (protein kinase, angiogene ...

Restriction endonucleases coupled with DNA methyltransferases form the restriction-modification (RM) systems that occur ubiquitously among bacteria. They protect bacterial cells against bacteriophage infection by cleaving incoming foreign DNA highly specifica ...

Pulmozyme� recombinant human deoxyribonuclease I (DNase I) is currently used as a therapeutic for cystic fibrosis (CF) (1) and may be effective in the treatment of systemic lupus erythematosus (SLE) (2,3). As described in Chapter 20, degradation of high-molecular-weight DNA following in ...

Human deoxyribonuclease (DNase I) is an important clinical agent currently used in the treatment of cystic fibrosis (CF) patients (1). It is inhaled into the airways, where it degrades DNA to lower molecular weight fragments, thus reducing the viscoelasticity of CF sputum and improving lung f ...

Reverse transcription is the process whereby the single-stranded RNA genome of a retrovirus is converted into double-stranded DNA by the DNA polymerase and ribonuclease H (RNase H) activities of virus-coded reverse transcriptase (RT) (2,16). The former activity of reverse transcrip ...

Ribonuclease A (RNase A), isolated from bovine pancreas, maintains a well-deserved place in the history of modern biochemistry, as many of the earliest studies on amino-acid sequencing, protein crystallography, and protein folding were performed on this stable and abundant protein (1). ...

Lectins, proteins that specifically bind carbohydrates, are widely distributed in animal and plant species. Functions of animal lectins include uptake of serum asialo-glycoproteins into liver, self-defense mechanisms, and modulation of cell-cell interactions during diff ...

Angiogenin is one of several unusual members of the pancreatic ribonuclease superfamily (for reviews see refs. 1,2). It was first isolated as a 14 kDa soluble protein from culture medium conditioned by human colon carcinoma (HT-29) cells, and identified as an angiogenic substance based on its c ...

Restriction endonucleases, which cleave DNA in a site-specific manner, are a fundamental tool of molecular biology. The discovery of endonucleases began in the 1960s and led to commercial availability in the early 1970s. The number of characterized enzymes continues to grow, as does the num ...

Toxins from plants and bacteria have been coupled to antibodies to produce selective cytotoxic agents (immunotoxins) (1–3). However, toxic side effects and immunogenicity have presented major obstacles to the successful clinical application of these proteins (4–9). Production of ...

Currently, there are approx 3000 restriction endonucleases known, recognizing 235 different sequences (1). Although primarily found in bacteria, they also exist in archaea, viruses, and eukaryotes. An estimated 25% of bacteria examined contain at least one restriction endonucle ...

Subcloning can be extraordinarily easy or extremely difficult. The simplest case requires cleavage of the desired fragment from the DNA in which it is located with one or two restriction enzymes, cleavage of the plasmid that will serve as the ultimate recipient with the same enzymes, and ligati ...

DNA-protein interactions are the basis for the molecular mechanisms responsible for nucleic-acid replication, gene transcription, recombination, viral integration, and gene regulation in both normal and pathophysiological conditions. Initially, deletional analys ...