Free energy perturbation techniques applied to subtilisin BPN' stability.

The inability to predict the effect of specific mutations on protein stability has been an area of concern to researchers in the field of protein engineering. Small stabilization free energies (5 to 15 kcal/mol) distinguish the native and the denatured states of a protein, making the rational design of protein stability a difficult challenge. Free Energy Perturbation Technique (FEPT) appears to be a method that will be important for protein engineering to meet this challenge. Not only is it a method to evaluate potential sites for mutation prior to synthesis, it identifies important atomic contributions that are responsible for the free energy changes of interest. Accuracy and speed are the principal limitations of the technique, but the powerful combination of structure, energy, dynamics and solvent make the investment of time and effort very attractive. Our examples illustrate both the power and limitations of FEPT. Using the program CHARMm, FEPT has been applied to the well known stabilizing mutations--asparagine to Serine--at residue 218 in subtilisin BPN'. In analyzing the atomic contributions that result in the increase in stability, two mutations at residue 203 were chosen to test the predictive power of FEPT. Sometimes extraordinary measures must be undertaken to sample sufficient conformational space to achieve accurate FEPT results. However we believe the method will be invaluable in the development of rules for designing a more stable subtilisin BPN'.

A simple technique for measurement of pressure in the tympanitic rumen of cattle.

The construction and method of use of a simple device for the non-invasive measurement of intra-rumenal pressure is outlined. Results obtained from calves suffering from increased intra-rumenal pressure (bloat) are shown. The method is capable of quantifying pressures involved in bloat and could be used to augment the visual assessment of bloat scoring.

An assessment of a method of manual pregnancy diagnosis in the ewe.

The recto-abdominal palpation method of ovine pregnancy diagnosis described by Hulet (1972) was carried out on 167 ewes in three flocks. The results showed a virtual 100 per cent accuracy of diagnosis between pregnancy and non-pregnancy and approximately 70 per cent overall accuracy in differentiating single from multiple pregnancies. At least 34 ewes aborted and five died. It was concluded that the method as carried out was neither safe nor accurate enough to justify any savings consequent upon more efficient food usage.

Effects on the oestrous cycle of dairy cows of the administration of colostrum in the mid-luteal phase.

A group of 13 cows were dosed orally nine or 10 days after a normal oestrous cycle; six animals received colostrum, five animals received milk containing varying amounts of oestrone sulphate, and two cows were given milk containing a low level of oestrone sulphate. Measurements of milk progesterone levels after dosing showed that colostrum had an apparent luteolytic effect, milk containing oestrone sulphate at a level of 2000 pg/ml had a less marked effect on milk progesterone and those animals receiving milk showed no reduction in milk progesterone. These results show that there is a physiological basis for the practice of inducing overt oestrus in cows showing no visible oestrus, by dosing them with colostrum.

Bem Sex-role Inventory stereotypes for men and women varying in age and race among National Register psychologists.

554 psychologists listed in the National Register of Health Care Providers in Psychology used the Bem Sex-role Inventory to rare a "mature, healthy, socially competent" individual in one of 18 target groups (a black or race-unspecified man, woman, or adult in their late 20s, late 40s, or late 60s). Factor analysis produced factors which generated three scales--nurturant, agentic, and self-governing. The attributes "feminine" and "masculine" were treated as individual items. Old targets were viewed as less agentic than younger targets and as less self-governing than the middle-aged. Female targets were perceived as more feminine and less masculine than were men. Interactions for agentic and self-governing suggest age and race and sex of target influence person perceptions.