forms appeared in the early 1980s. Some lyophilized preparations approach 98% purity or more but rarely match the >99% achieved by extremely pure solutions. Generally, solution nucleotides are purer than the lyophilized version, but unless supporting quality control data are provided, it should not be concluded that a solution nucleotide is extremely pure or even more pure than a yophilized preparation Are Solution Nucleotides More Stable Than Lyophilized Nucleotides? Peparations of deoxynucleoside triphosphates decompose into nucleoside di- and tetraphosphates via a disproportionation reaction. This reaction is concentration and temperature dependent. At temperatures above 4oC, lyophilized prepara- tions of deoxynucleotides undergo disproportionation faster than nucleotides in solution. In contrast, the rate of degradation for both forms is less than 1% per year at -20oC and below(Table 10.1). Solutions of dideoxynucleotides and ribonucleotides are similarly stable for many months at temperatures of -20C and below. Most, but not all, dideoxy- and ribonucleotides are stable for many months at4°C Table 10. I Storage Stability of Nucleotides Triphosphate Form Months 70°C 2 dATP 99.14 9747 95.46 3945 (275) (1.75) dTTP 97.2 9428 3945 (30mo) (2.75mo) duTP NA NA NA Solution (100mM) dATP 98.75 91.8 (2mo) 37.07 dCTP 9938 (2mo) 21.25 270 Gersteinforms appeared in the early 1980s. Some lyophilized preparations approach 98% purity or more but rarely match the >99% achieved by extremely pure solutions. Generally, solution nucleotides are purer than the lyophilized version, but unless supporting quality control data are provided, it should not be concluded that a solution nucleotide is extremely pure or even more pure than a lyophilized preparation. Are Solution Nucleotides More Stable Than Lyophilized Nucleotides? Peparations of deoxynucleoside triphosphates decompose into nucleoside di- and tetraphosphates via a disproportionation reaction. This reaction is concentration and temperature dependent. At temperatures above 4°C, lyophilized prepara￾tions of deoxynucleotides undergo disproportionation faster than nucleotides in solution. In contrast, the rate of degradation for both forms is less than 1% per year at -20°C and below (Table 10.1). Solutions of dideoxynucleotides and ribonucleotides are similarly stable for many months at temperatures of -20°C and below. Most, but not all, dideoxy- and ribonucleotides are stable for many months at 4°C. 270 Gerstein Table 10.1 Storage Stability of Nucleotides % Triphosphate Form Months -70°C -20°C 4°C 21°C Powder dATP 54 99.44 99.14 97.47 93.93 (48 mo) 97.78 (3 mo) dCTP 54 98.46 95.46 39.3 39.45 (33 mo) (2.75) dGTP 54 96.95 95.37 25.74 34.4 (27 mo) (1.75) dTTP 54 97.29 94.28 27.4 39.45 (30 mo) (2.75mo) dUTP N.A. N.A. N.A. N.A. N.A. Solution (100 mM) dATP 54 99.2 98.75 95.3 91.8 (2 mo) 37.07 (39 mo) dCTP 54 99.38 99.15 96.98 95.2 (2 mo) 21.25 (42 mo)