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  • Nucleic acid structure, Phsyical and Biochemical Characterisation of DNA  (2)
  • 13C NMR  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 26 (2000), S. 2119-2140 
    ISSN: 1573-1561
    Keywords: Polyphenols ; condensed tannins ; plant adaptations ; plant–litter-soil interactions ; 13C NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract There is a resurgence of interest in the quantification of polyphenols in plant tissues because of their presumed ecological importance in plant–litter–soil and plant–animal interactions. The influence of sample preparation, extracting solvent, foliage quality, and assay method was investigated for the quantification of total phenols and condensed tannins in conifer foliage. Our results suggest that it is not possible to recommend a single optimal protocol for quantification of total phenol and condensed tannin fractions from plant materials. In general, the use of aqueous acetone (50–70% v/v) with freeze-dried materials gave the highest recovery. The Folin-Ciocalteau method for total phenols and the butanol–HCl hydrolysis method for condensed tannins appear superior to other common assays tested. There were large differences (1.4–2.2 times) in the reactivity of purified condensed tannins among species, indicating the importance of an appropriate standard for polyphenol quantification. A solid-state 13C NMR method with an improved "interrupted decoupling" pulse sequence yielded the highest concentrations for condensed tannins. Assuming that 13C NMR provides an accurate measure of total condensed tannin, the other extraction/assay methods used in this study recovered 50–86% of the condensed tannin fraction. The recovery rate is correlated with the nitrogen content of the foliage, which suggests that the formation of protein–tannin complexes may limit the extractability of condensed tannins. While 13C NMR condensed tannin values may give the best value for total condensed tannin concentrations, the water-soluble fraction may have the greatest physiological and/or ecological significance.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-01-09
    Description: Due to the long-range nature of high-order interactions between distal components in a biomolecule, transition dynamics of tertiary structures is often too complex to profile using conventional methods. Inspired by the exploded view in mechanical drawing, here, we used laser tweezers to mechanically dissect high-order DNA structures into two constituting G-quadruplexes in the promoter of the human telomerase reverse transcriptase (hTERT) gene. Assisted with click-chemistry coupling, we sandwiched one G-quadruplex with two dsDNA handles while leaving the other unit free. Mechanical unfolding through these handles revealed transition dynamics of the targeted quadruplex in a native environment, which is named as native mechanical segmentation (NMS). Comparison between unfolding of an NMS construct and that of truncated G-quadruplex constructs revealed a quadruplex–quadruplex interaction with 2 kcal/mol stabilization energy. After mechanically targeting the two G-quadruplexes together, the same interaction was observed during the first unfolding step. The unfolding then proceeded through disrupting the weaker G-quadruplex at the 5'-end, followed by the stronger G-quadruplex at the 3'-end via various intermediates. Such a pecking order in unfolding well reflects the hierarchical nature of nucleic acid structures. With surgery-like precisions, we anticipate this NMS approach offers unprecedented perspective to decipher dynamic transitions in complex biomacromolecules.
    Keywords: Nucleic acid structure, Phsyical and Biochemical Characterisation of DNA
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 3
    Publication Date: 2015-01-10
    Description: Structural features of nucleic acids have become an integral part of current biomedical research. Highly selective and readily performed methods with little toxicity that target guanosines in non-duplex nucleic acids are needed, which led us to search for an effective agent for guanosine sequencing. Treatment of DNA or RNA with potassium tungstate and hydrogen peroxide produced damaged guanosines in DNA or RNA sequences. The damaged guanosines in non-duplex DNA could be cleaved by hot piperidine. Similarly, damaged guanosines in non-duplex RNA could be cleaved by aniline acetate. We could identify structural features of nucleic acid using this strategy instead of dimethyl sulphate and Ribonuclease T1.
    Keywords: Nucleic acid structure, Phsyical and Biochemical Characterisation of DNA
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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