TIBTECH - FEBRUARY 1986

33 Newell, R. D. (1980) in Biological Microcalorimetry (Beezer, A. E. ed.), pp. 163-186, Academic Press

34 Beezer, A. E. and Chowdhry, B.Z. (1980) in Biological Microcalorimetry (Beezer, A.E. ed.), pp. 195-246, Academic Press

35 Beezer, A. E. and Chowdhry, B.Z.

(1980) Talanta 27, 1-5 36 Gram, L. and S~gaard, H. (1985)

Thermochim. Acta 95, 373-381 37 Mou, D-G. and Cooney, C. L. (1976)

Biotech. Bioeng. 18, 1371-1392 38 Monti, M., Brandt, L., Ikomi-Kumm,

J., Ohlsson, H. and Wads6, I. (1981) Scand. ]. HaematoI. 27,305-310

39 Monti, M. in Thermal and Energetic Studies o f Cellular Biological Sys- tems (James, A. M.ed.), Adam Hilger (in press)

40 Kemp, R. B. in Thermal and Energetic Studies o f Cellular Biological Sys- tems (James, A. M., ed.), Adam Hilger, (in press)

I m p r o v e d m e t h o d for e s t i m a t i n g D N A size us ing

gel e l ec t rophores is The relative mobility in agarose gel electrophoresis of plasmids ranging in size from 1.37 to 312 MDa was measured under different electrophoretic condi- tions. It was found that a multiple regression (log10 molecular size against log10 relative mobility and the reciprocal square root of the relative mobility) gave a good fit to all the data: errors in estimates of molecular sizes were low (~<3.0 + 1.5%):

log10 Mr = a + bl (logier) + b2r -I/2

The multiple regression method rep- resents a considerable improvement over existing electrophoresis analysis methods and will be particularly advan- tageous for estimating the size of larger plasmids, existing methods for which are either inaccurate or intricate and time- consuming.

It is suggested that using the multiple regression methods with the eight plas- mids of E. cell V517 and the large plasmid TP116 of E. cell IR713 will provide a simple and rapid method for determining the size of bacterial plas- mids and other covalently closed circu- lar DNA. The method also gives an improved estimation of restriction frag- ment sizes.

Rochelle, P. A., Fry, J.C., Day, M.J. and Bate, M.J. (1986) ]. Gen. Micro- biol. 132, 53-59

Less e x p e n s i v e o l i g o n u c l e o t i d e s y n t h e s i z e r *

Pharmacia are offering a fully automated oligonucleotide synthesizer which has an integral monitoring system allowing

calculation of coupling efficiency during synthesis, The Gene Assembler TM uses [~-cyanoethylamidite chemistry and i s

claimed to provide a coupling efficiency of greater than 98% with cycle times of 9.7 min. The reagents are delivered by a peristaltic pump system. The company believes the Gene Assembler TM offers the technical capability of other machines on the market but is lower in price (approx. $25 000/£16 000).

*Entries marked with asterisks are based on information supplied by manu- facturers.

T r a n s f e c t i o n of Curynebacterium l i l ium

A transfection method for the lysine- producing bacterium, Corynebacterium ]ilium, has been developed. Treatment of the culture with ampicillin prior to lysozyme treatment was required to obtain protoplasts efficiently. DNA from the C. l i l ium bacteriophage CL31 was mixed with protoplast suspensions fol- lowing various times of lysozyme treat- ment. The ratio of transfectants ta regenerable cells rose to a maximum of 6×10 -3 after 20 h (the ratio of transfect- ants to the number of cells treated with lysozyme reached a maximum of 4 × 10 -5 after 20 h - a large proportion of the population is not regenerable).

Yeh, P., Oreglia, J. and Sicard, A. M. (1985) ]. Gen. Microbiol. 131, 3179-3183

(~ 1986, Elsevier Science Publishers B.V., Amsterdam 0166 - 9430/86/$02.00