Hydrazine frequency shifts

Upon evacuation of the KH complex to 10 7 atm, the bulkv(N-H) bands at 3196 and 3336 cm 1 are strongly reduced in intensity and shifted up in frequency to 3225 and 3361 cm 1, respectively. The close agreement between the band positions of the v(N-H) bands of the KH complex (Fig. 5b) and those of liquid hydrazine (23) indicate that much of the hydrazine present on the sample at 1 atm. pressure (Figs. 2b, 5b) is physically adsorbed on the external surfaces of kaolinite. The weight-loss data of the KH complex indicate that a significant portion of the hydrazine is... 

The DNA sequencing chemistry begins with a base-modification reaction, the extent of which determines the frequency of DNA cleavage in the subsequent phosphate-elimination reaction. The number of bases modified in each molecule depends on the concentration of dimethylsulphate (G and G A reactions) and hydrazine (C T reactions) as well as the temperature and duration of the reaction. For speed and convenience the Maxam-Gilbert procedure makes use of temperature shifts and dilution to control the rate and extent of these reactions. The reagents are mixed at 0°C, incubated at 20°C for the required time and the DNA precipitated with cold sodium acetate and ethanol to slow down or halt the reaction. A fixed concentration of the different reagents is usually used so the main factor determining the extent of reaction is the time of incubation at 20°C. 

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