Nucleic acids determination

II A radically different type of nucleoprotein is that provided by the smaller RNA viruses of the elongated spiral type like tobacco mosaic, or of the polyhedral type such as tomato bushy stunt, tipula virus or poliomyelitis virus. The only one of these adequately studied has been tobacco mosaic virus, Franklin [19, 20], and here it appears that the protein and not the nucleic acid determines the structure. There is only one RNA chain and this is wound helically so that one protein is in contact with three successive nucleotides. 

J. Wang, X. Cai, B. Tian and H. Shiraishi, Microfabricated thick-film electrochemical sensor for nucleic acid determination, Analyst, 121 (1996) 965-970. 

Advancements in the area of optical biosensors for nucleic acid determinations have been substantial and many design concepts and surface chemistries have been explored. A practical solution that provides for all of the desired biosensor attributes - reusability, robustness, reliability, selectivity, sensitivity and speed of response - in a single device has not yet been... 

For research on proteins, this article will only cover antibody-based technologies. The limitation in biological sample volume and the inabihty to amphfy unknown proteins in a similar fashion as nucleic acids determines the type of array. Another limitation is the cross-reactivity of proteins and antibodies that do not allow multiplexed probing of a complex biological mixture with more than 30 to 40 antibodies with sufficient sensitivity. 

The molar ratio of cationic liposome to nucleic acid determines the proportion of electrostatic neutralization, which reflects the entire surface charge and the size of resulting lipoplexes (13). Therefore, lipoplex formation should be affected by experimental variables such as nucleic acid/cationic liposome concentration, time and medium for the complexation, the number and/or order of addition steps, and the presence of serum during lipoplex formation. In this section, we will present instructions to form lipoplexes and discuss the most important aspects to be considered in siRNA- or pDNA-lipoplex formation. 

The yeast prion hypothesis provides explanations for several unique characteristics of [PSP] that were inconsistent with a nucleic acid determinant (Wickner, 1994). 

Eshar Z, Benacerraf B, Katz DH (1975) Induction of tolerance to nucleic acid determinants by administration of a complex of nucleoside D-glutamic acid and D-lysine (D-GL). J Immunol 114 872-876... 

In this section several examples of genosensors based on hybridization event, which have been constructed on screen-printed electrodes, will be described. One of them has been designed to detect a 30-mer SARS (severe acute respiratory syndrome) virus sequence whilst the others have been designed to identify the nucleic acid determinants exclusively present on the genome of the pathogen Streptococcus pneumoniae. 

Once the procedure was optimized, an enzymatic genosensor for the identification of a nucleic acid determinant exclusively present on the genome of the pathogen S. pneumoniae was developed. This DNA sensor has been described and optimized by our research group in the previous section. In this work, for the electrochemical detection step, 3-IP was used as substrate and then sulfuric acid was added to generate an electroactive compound termed indigo carmine, which is quantified by cyclic voltammetry. 

It is beyond the scope of this chapter to discuss all available technologies, just one example of each of three detection principles will be mentioned here, viz., a growth based method, a non-growth based method and a nucleic acid determination method. For an encyclopaedic overview the reader is referred to the literature [71]. 

The most obvious approach is to digest with a nuclease the cross-linked protein-nucleic acid complex so as to remove regions of the nucleic acid that are not cross-linked to the protein. However, discretion must be exercised in the choice of nuclease. For example, a nonspecific nuclease, such as T2 ribonuclease, is of little value since it may leave only mononucleotide units attached to the protein. Because the four common nucleotides are distributed throughout the nucleic acid, determination of... 

How do nucleic acids determine cell reproduction Each time a cell (or virus) reproduces itself, it transmits the ability to continue the reproduction. The reliability of this transmittal accounts for the continuity of species. It is therefore reasonable to assume that some sort of durable pattern is preserved or reconstructed with each duplication. A pattern is a physical entity whose size, shape, and makeup carry information, such as a punched card, a dress pattern, or a perforated metal plate that establishes the positions of boltholes. In the cell nucleus, the reproduction pattern is the DNA molecule. The sequence of bases embodies the pattern, or code, for the synthesis of proteins. For brevity, let us designate the bases by their initials, A, C, C, and T, as shown in Fig. 26.10. Now if we imagine that a single DNA strand were isolated, and stretched out along a straight line, we would have a structure such as... 

Nucleic acid determination is another method for biomass determination. The DNA content in the medium depends on the growth of biomass. 

The three ternary complexes of SNase formed respectively with pdTp, pdGp, and PNP-pdTp display quite similar conformational features in NMR, suggesting that the conformation of the enzyme is not strongly dependent on whether the 5 -P is a mono- or diester (55). The conformational features of the bound nucleic acid determine the differences in catalytic rates between substrates. In the ternary complex, e.g., enzyme-Co -dTdA, evidence suggests that the metal induces conformational changes both at the attacked phosphorus and at the leaving group of the enzyme-bound substrate (5). 

Electrochemical methods not only facilitate the development of DNA biosensors which have led to a lot of advantages mentioned above but also different possibilities in the fields, such as contemporary nucleic acid research, DNA-protein interactions, DNA damage, highly sensitive nucleic acid determination, effect of surface charge on the structure and properties of DNA adsorbed at the surface, highly sensitive detection of impurities in DNA samples, etc. Electrochemical research on DNA is a vast field requiring more researchers with some knowledge both in electrochemistry and biochemistry of nucleic acids. 

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