Serine octamer as a unique “magic-number” cluster in the gas phase, has been extensively studied by experimentalists and theorists since its discovery in mass spectrometry in 2001. It is characterized by a pronounced preference of homochirality. Interestingly, the chirality of serine octamer can transfer to other molecules through enantioselective substitution reactions. Thus it is suggested that it might be related to the origin of our homochiral world. In this review, all the results and progresses in the formation, structure and chiral signature of serine octamer and substituted serine octamer over the past years are summarized. Different methods, including mass spectrometry with different ionization sources, gas phase H/D exchange, ion mobility, infrared photodissociation spectroscopy, and theoretical calculations are applied for the cluster ions. Different characteristics of the magic cluster are discovered gradually, helping us to have a deep insight into its structure and role in chiral recognition and transmission. However, due to the complexity of the system, it is still a big challenge to understand its true structure, the reason of its performance in homochirality and its role in the origin of biomolecular homochirality.
Contents
1 Introduction
2 Generation of serine octamer
2.1 Electrospray
2.2 Other spray-based ionization method
2.3 Evaporation and sublimation
2.4 Other method
2.5 Mechanism
3 Structural studies
3.1 MS/MS
3.2 Gas-phase H/D exchange
3.3 Ion mobility
3.4 IRPD spectroscopy
3.5 Theoretical calculation
4 Substituted serine octamers
4.1 Substituted by other amino acids
4.2 Substituted by sugars
4.3 Other relative clusters
5 Chiral characteristic
5.1 Enantiometic enrichment and chiral transmission
5.2 Chiral differentiation
5.3 Discussion
6 Conclusion