Interactive Crystallomic - Molecules: Nucleation, Aggregation and Crystallization - page 228

drop is clear immediately after it was created, to simultaneously vary the
virus (or protein) concentration and the concentration of precipitate.

Algorithm

The sequence of steps involved in setting up crystallization drops can be
described as follows:

START
CHOOSE precipitant

1 IF FOR EXPERIMENT n OUTCOME = Yp

THEN
APPLY X1 = [ C v ( n + 1)] ∗ [ C p ( n + 1)] < [ C v ( n )] ∗ [ C p ( n )] FOR

EXPERIMENT n + 1

IF OUTCOME = Yo THEN GOTO 1

OTHERWISE
APPLY X2 = [ C v ( n + 1)] ∗ [ C p ( n + 1)] > [ C v ( n )] ∗ [ C p ( n )] FOR

EXPERIMENT n + 1

CONTINUE
END

The immediate outcomes after creating a drop n are classified as either Yp
or Yo. When the drop is clear, it is classified as Yo; when the drop is not
clear (because of precipitation or phase separation), it is classified as Yp.
In the subsequent experiment ( n 1), the condition X1 is applied such that

the product of the multiplication of the concentrations of the virus-like
particles and the precipitant for experiment ( n

+

1) is smaller than the
same product for experiment n . In other words, X1 satisfies the equation
[ C v ( n

+

[ C v ( n )] * [ C p ( n )], where C v ( n ) and C p ( n ) are
the concentrations (mg/ml) of the virus and the precipitant (w/v, % or M)
respectively. However, if the outcome of the drop from experiment ( n

+ 1)] * [ C p ( n + 1)] <

1)
is Yo and the drop is clear, then the experiments are terminated. If the out-
come of the drop is not Yo, then the condition X2 is applied such that the
product of the concentrations (virus and precipitant) for experiment ( n

+

+ 1)