pH-Dependent Adsorption of Peptides on Montmorillonite for Resisting UV Irradiation.

Ultraviolet (UV) irradiation is considered an energy source for the prebiotic chemical synthesis of life's building blocks. However, it also results in photodegradation of biology-related organic compounds on early Earth. Thus, it is important to find a process to protect these compounds from decomposition by UV irradiation. Herein, pH effects on both the adsorption of peptides on montmorillonite (MMT) and the abilities of peptides to resist UV irradiation due to this adsorption were systematically studied. We found that montmorillonite (MMT) can adsorb peptides effectively under acidic conditions, while MMT-adsorbed peptides can be released under basic conditions. Peptide adsorption is positively correlated with the length of the peptide chains. MMT's adsorption of peptides and MMT-adsorbed peptide desorption are both rapid-equilibrium, and it takes less than 30 min to reach the equilibrium in both cases. Furthermore, compared to free peptides, MMT-adsorbed peptides under acidic conditions are well protected from UV degradation even after prolonged irradiation. These results indicate amino acid/peptides are able to concentrate from aqueous solution by MMT adsorption under low-pH conditions (concentration step). The MMT-adsorbed peptides survive under UV irradiation among other unprotected species (storage step). Then, the MMT-adsorbed peptides can be released to the aqueous solution if the environment becomes more basic (releasing step), and these free peptides are ready for polymerization to polypeptides. Hence, a plausible prebiotic concentration-storage-release cycle of amino acids/peptides for further polypeptide synthesis is established.

Copper-Catalyzed Direct Twofold C-P Cross-Coupling of Unprotected Propargylic 1,4-Diols: Access to 2,3-Bis(diarylphosphynyl)-1,3-butadienes.

The first facile and efficient Cu-catalyzed direct coupling of unprotected propargylic diols with H-phosphine oxides was developed, providing a practical approach to access structurally diverse 2,3-bis(diarylphosphynyl)-1,3-butadienes along with the formation of two new P-Csp2 and two new C═C bonds under ligand- and base-free conditions.

A ''turn-off'' SERS assay for kinase detection based on arginine N-phosphorylation process.

A sequential "turn-off" surface enhance Raman scattering (SERS) assay platform for the detection of protein arginine kinase McsB is constructed based on arginine N-phosphorylation process. The positive charged peptide initiates the aggregation of labelled Au nanoparticles (AuNPs) to form ''Hot Spots'', resulting to a higher SERS intensity. However, the aggregation of AuNPs could also be disbanded by the addition of McsB in which the peptides are phosphorylated on arginine residues, leading to the sharp decline of SERS signal, on account of two negative charges on the phosphate group. By this strategy, a novel ''turn-off'' SERS biosensor for McsB detection based on arginine N-phosphorylation was established with high sensitivity, selectivity and simplicity. Compared with other non-enzymatic amplification methods, the sensitivity of this newly demonstrated method was improved effectively. The detection limit for McsB is 46 pM. Besides, some controlled experiments show that the assay possesses good selectivity, which is mainly decided by the specificity of kinase. Since some kinases are important biomarkers, this assay could make great contribution in biomarkers detection in complex matrices which is based on signal amplification.

Cobalt-Catalyzed Oxidative C(sp3)-H Phosphonylation for α-Aminophosphonates via C(sp3)-H/P(O)-H Coupling.

The first oxidative C(sp3)-H phosphonylation of tertiary aliphatic amines has been developed. The use of cobalt acetate as a catalyst, N-hydroxyphthalimide as a cocatalyst, and air as an oxidant enabled the conversion of tertiary aromatic and aliphatic amines into α-aminophosphonates in moderate to excellent yields under mild conditions via a cross dehydrogenative coupling reaction.

Prebiotic formation of cyclic dipeptides under potentially early Earth conditions.

Cyclic dipeptides, also known as 2,5-diketopiperazines (DKPs), represent the simplest peptides that were first completely characterized. DKPs can catalyze the chiral selection of reactions and are considered as peptide precursors. The origin of biochemical chirality and synthesis of peptides remains abstruse problem believed to be essential precondition to origin of life. Therefore, it is reasonable to believe that the DKPs could have played a key role in the origin of life. How the formation of the DKPs through the condensation of unprotected amino acids in simulated prebiotic conditions has been unclear. Herein, it was found that cyclo-Pro-Pro could be formed directly from unprotected proline in the aqueous solution of trimetaphosphate (P3m) under mild condition with the yield up to 97%. Other amino acids were found to form proline-containing DKPs under the same conditions in spite of lower yield. During the formation process of these DKPs, P3m promotes the formation of linear dipeptides in the first step of the mechanism. The above findings are helpful and significant for understanding the formation of DKPs in the process of chemical evolution of life.