Thermodynamic measurements are reported for 51 DNA duplexes with A.A, C.C, G.G, and T.T single mismatches in all possible Watson-Crick contexts. These measurements were used to test the applicability of the nearest-neighbor model and to calculate the 16 unique nearest-neighbor parameters for the 4 single like with like base mismatches next to a Watson-Crick pair. The observed trend in stabilities of mismatches at 37 degrees C is G.G > T.T approximately A.A > C.C. The observed stability trend for the closing Watson-Crick pair on the 5' side of the mismatch is G.C >/= C.G >/= A.T >/= T.A. The mismatch contribution to duplex stability ranges from -2.22 kcal/mol for GGC.GGC to +2.66 kcal/mol for ACT.ACT. The mismatch nearest-neighbor parameters predict the measured thermodynamics with average deviations of DeltaG degrees 37 = 3.3%, DeltaH degrees = 7. 4%, DeltaS degrees = 8.1%, and TM = 1.1 degrees C. The imino proton region of 1-D NMR spectra shows that G.G and T.T mismatches form hydrogen-bonded structures that vary depending on the Watson-Crick context. The data reported here combined with our previous work provide for the first time a complete set of thermodynamic parameters for molecular recognition of DNA by DNA with or without single internal mismatches. The results are useful for primer design and understanding the mechanism of triplet repeat diseases.

The thermodynamic contributions to duplex formation of all 32 possible single-nucleotide dangling ends on a Watson-Crick pair are reported. In most instances, dangling ends are stabilizing with free energy contributions ranging from +0.48 (GT(A)) to-0.96 kcal/mol (). In comparison, Watson-Crick nearest-neighbor increments range from -0. 58 (TA/AT) to -2.24 (GC/CG) kcal/mol. Hence, in some cases, a dangling end contributes as much to duplex stability as a Watson-Crick A-T base pair. The implications of these results for DNA probe design are discussed. Analysis of the sequence dependence of dangling-end stabilities show that the nature of the closing base pair largely determines the stabilization. For a given closing base pair, however, adenine dangling ends are always more or equally as stable as the other dangling nucleotides. Moreover, 5' dangling ends are more or equally as stabilizing as their 3' counterparts. Comparison of DNA with RNA dangling-end motifs shows that DNA motifs with 5' dangling ends contribute to stability equally or more than their RNA counterparts. Conversely, RNA 3' dangling ends contribute to stability equally or more than their DNA counterparts. This data set has been incorporated into a DNA secondary structure prediction algorithm (DNA MFOLD) (http://mfold2.wustl.edu/mfold/dna/for m1.cgi) as well as a DNA hybridization prediction algorithm (HYTHERtrade mark) (http://jsl1.chem.wayne.edu/Hyther/hythermenu .html).

Distributions of melting temperature (Tm), free energy (DeltaG(T)o), and fraction hybridized or fraction bound (Fb), are presented for oligos of length 10-50 bases sampled from the human genome. The effects of changing temperature, oligo and salt concentrations, constraining G+C content, and introducing mismatches are exemplified. Our results provide the first survey of typical and limiting thermodynamic values evaluated on a genomic scale. Described numbers comprise useful 'rules of thumb' that are applicable to most technologies dependent upon DNA oligo design.

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International audienceThe friction between interfaces at bolted joints plays a major role in the damping of structures. This paper deals with the energy losses caused by micro-slips in the joints. The aim of this study is to define in an analytical way these energy dissipation mechanisms which we examine through the analysis of a new benchmark: the flexural vibration of a clamped-clamped beam with original positioning of the interfaces. The joints exhibit the behavior of an interface under constant and uniform normal stress. The stress and strain values are computed at the joints under the assumption of quasi-static motion. This model allows us to understand the evolution of the slip and stick regions along the joint interfaces during the loading process. The expressions of the strain and stress fields during each phase of the loading process are derived. These lead to the quantification of the dissipated energy within the interface. Using this formula, a nonlinear loss factor can then be computed. In the final part of the paper, the dynamic response of the beam is calculated using this nonlinear loss factor