So far, you have discussed chirality amplification. This theory will requires a

Question

So far, you have discussed chirality amplification. This theory will requires a small excess of one enantiomer to begin the amplification process. In this question set you will discuss how that original excess appeared. One (disputed) theory of the original genesis of "chiral molecules" on Earth comes from outer space. The Murchison meteorite, which fell to earth in Australia in 1969. was shown to contain trace, of amino acids and other simple organic materials. These material, displayed a 'slightly enhanced" enantiomeric ratio. i.e.. more of one enantiomer than the other (Engel & Macko 1997; Cronin & Pozzarello 1997). The theory 'was posited that similarly material, crashed to earth during the prebiotic period (Pizzarello & Groy 2011) The presence of natural amino acids with enhancement of the L isomer. Discuss why the observation of un natural amino acids such as these is less susceptible to false positives than the presence of alanine above. Assume that there was an excess of (L)-isovaline conferring chirality on species such as 1, based on your reading of noorduin, et, al.

Explanation / Answer

a. The presence of natural amino acids with enantiomeric excess from the meteorite is still a subject of debate because because amino acids that could be extracted from these rocks appear to be contaminated by terrestrial organic material.

The experimental issues with stating that alanine found on the Murchison meteorite has an excess of one (L) enantiomer is that the meteors' chiral amino acids tend to occur in racemic mixtures i.e.,

the lab experiments designed to simulate abiotic synthesis in the solar system results in racemic mixtures of amino acids.

The "false positives" observed in the analysis of these meteorite samples is due to the contamination has occurred through exposure, storage, or handling.

b. The observation of unnatural amino acids, isovaline is less susceptible to false positives than the presence of alanine because these cannot be the result of interference from other C5 amino acid isomers present in the samples, analytical biases or contaminated through exposure, storage, or handling.

c. Noorduin, et al., have demonstrated the enantiomeric enhancement upon crystallization by using amino acid surrogate 1. The treatment of 1 with base illustrated the racemization in solution upon. Hence, the plausibility of (L)-isovaline conferring chirality on species such as 1 is less likely. Because upon addition of a base (L)-isovaline will racemize.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.