What do you mean by "law of probability is 10 to the 50th power"? It is a meaningless statement to me.
It's a meaningless statement to anybody, but some people understand where it comes from. Juhrahnimo's referring to
Borel's "Law". Borel's law is not a law, it's a rule of thumb, and the common creationist choice of 1 in 10
50 as a probability level which divides the possible from the essentially impossible is not supported by Borel's work or any science or mathematics. As you no doubt know, the choice of a probability level at which we ignore the possibility of some event happening depends on the situation.
The latest practitioner of this claptrap is William Dembski with his "universal probability bound".
A simple demonstration how sily any universal probablity bound is: take two decks of cards, shuffle them, and lay the cards out on a table in a line. The probability of the arrangement you are looking at, before you laid out the cards, was 1 in 10
166. But it happened. For more improbable events, add more decks of cards.
Of course, this is a digression from the real point, which is that nobody thinks that left-handed amino acids came to be or joined to form proteins by chance; they did so in acordance with the laws of chemistry and the surrounding environment (catalytic surfacesa and the like). We don't yet have a good theory of how it happened, but "chance" isn't even in the runnning.