Ion Mobility Mass Spectrometry Measures the Conformational Landscape of p27 and its Domains and how this is Modulated upon Interaction with Cdk2/cyclin A

Intrinsically disordered proteins have been reported to undergo disorder‐to‐order transitions upon binding to their partners in the cell. The extent of the ordering upon binding and the lack of order prior to binding is difficult to visualize with classical structure determination methods. Binding of p27 to the Cdk2/cyclin A complex is accompanied by partial folding of p27 in the KID domain, with the retention of dynamic behavior for function, particularly in the C‐terminal half of the protein. Herein, native ion mobility mass spectrometry (IM‐MS) is employed to measure the intrinsic dynamic properties of p27, both in isolation and within the trimeric complex with Cdk2/cyclin A. The trimeric Cdk2/cyclin A/p27‐KID complex possesses significant structural heterogeneity compared to Cdk2/cyclin A. These findings support the formation of a fuzzy complex in which both the N‐ and C‐termini of p27 interact with Cdk2/cyclin A in multiple, closely associated states.     

Orthogonal Halogen‐Bonding‐Driven 3D Supramolecular Assembly of Right‐Handed Synthetic Helical Peptides

Peptide‐mediated self‐assembly is a prevalent method for creating highly ordered supramolecular architectures. Herein, we report the first example of orthogonal C?X???X?C/C?X???π halogen bonding and hydrogen bonding driven crystalline architectures based on synthetic helical peptides bearing hybrids of l ‐sulfono‐γ‐AApeptides and natural amino acids. The combination of halogen bonding, intra‐/intermolecular hydrogen bonding, and intermolecular hydrophobic interactions enabled novel 3D supramolecular assembly. The orthogonal halogen bonding in the supramolecular architecture exerts a novel mechanism for the self‐assembly of synthetic peptide foldamers and gives new insights into molecular recognition, supramolecular design, and rational design of biomimetic structures.     

Morphological characterization of the antennal sensilla of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), with reference to their probable functions

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is one of the most significant economic pests of citrus worldwide. This insect vectors three phloem-restricted bacteria in the genus Candidatus Liberibacter that cause huanglongbing (citrus greening), the most severe disease limiting citrus production worldwide. We examined the external morphology of the antennal sensilla of male and female D. citri using scanning electron microscopy (SEM) and determined the putative functions of the identified sensilla using transmission electron microscopic (TEM) techniques. The filiform antennae of D. citri were of the conventional type comprised of a basal scape, pedicel and a long, thread-like flagellum, which is composed of eight flagellomeres. Eleven morphologically unique sensillar types were found and described on the antennae of male and female D. citri. Of those identified, the two apical setae, multiporous types I and II sensilla trichoidea, and the antennal rhinaria were porous and may be involved in perception of host- and mate-related volatile chemicals. However, the aporous types I, II and III sensilla trichoidea may have mechanosensory functions and the chaetica sensilla, cavity sensilla and unidentified uniporous sensilla may be involved in proprioception, thermo-hygroreception and cold detection, respectively. The shape, external morphology and array of sensilla on the antennae of male and female D. citri were similar. The only major difference observed was in the morphology of the short apical setae, whose tips were recessed inward in females but not so in males. The results are discussed in relation to plausible roles of the identified sensilla in mate and host location by this species.     

Sulfono‐γ‐AApeptides as a New Class of Nonnatural Helical Foldamer

Foldamers offer an attractive opportunity for the design of novel molecules that mimic the structures and functions of proteins and enzymes including biocatalysis and biomolecular recognition. Herein we report a new class of nonnatural helical sulfono‐γ‐AApeptide foldamers of varying lengths. The crystal structure of the sulfono‐γ‐AApeptide monomer S6 illustrates the intrinsic folding propensity of sulfono‐γ‐AApeptides, which likely originates from the bulkiness of tertiary sulfonamide moiety. The two‐dimensional solution NMR spectroscopy data for the longest sequence S1 demonstrates a 10/16 right‐handed helical structure. Optical analysis using circular dichroism further supports well‐ defined helical conformation of sulfono‐γ‐AApeptides in solution containing as few as five building blocks. Future development of sulfono‐γ‐AApeptides may lead to new foldamers with discrete functions, enabling expanded application in chemical biology and biomedical sciences.     

Zn(II) ions bind very efficiently to tandem repeat region of "prion related protein" (PrP-rel-2) of zebra-fish. MS and potentiometric evidence

Multi-histidine peptide fragments of zebra-fish prion protein are effective ligands for Zn(II) ions. Moreover the formation of a dinuclear complex species with a longer peptide can suggest the existence of the cooperative effect in the metal ion binding.     

Reactivity of a heterocyclic As-Se compound with metal salts: syntheses and structures of the first copper complexes and of new alkali metal salts containing As-Se anions

The structures of the new compounds [Cu8(Ph2As2Se2)2(PhAsSe2)2(dppm)4] (1) (dppm = bis-diphenylphosphinomethane), [Cu4(Ph2As2Se2)2(PPh3)4] (2), [{K(18-crown-6)}2(PhAsSe3)] (3), [Na12(PhAsSe3)6(15-crown-5)6] (4) and 1/x[Na2(PhAsSe3)(thf)(H2O)3]x (5) are reported. 2-5 were prepared by reactions of metal thiolates with [(PhAs)2(mu-Se)(mu-Se2)].     

Prediction of protein structural class using novel evolutionary collocation-based sequence representation

Knowledge of structural classes is useful in understanding of folding patterns in proteins. Although existing structural class prediction methods applied virtually all state-of-the-art classifiers, many of them use a relatively simple protein sequence representation that often includes amino acid (AA) composition. To this end, we propose a novel sequence representation that incorporates evolutionary information encoded using PSI-BLAST profile-based collocation of AA pairs. We used six benchmark datasets and five representative classifiers to quantify and compare the quality of the structural class prediction with the proposed representation. The best, classifier support vector machine achieved 61-96% accuracy on the six datasets. These predictions were comprehensively compared with a wide range of recently proposed methods for prediction of structural classes. Our comprehensive comparison shows superiority of the proposed representation, which results in error rate reductions that range between 14% and 26% when compared with predictions of the best-performing, previously published classifiers on the considered datasets. The study also shows that, for the benchmark dataset that includes sequences characterized by low identity (i.e., 25%, 30%, and 40%), the prediction accuracies are 20-35% lower than for the other three datasets that include sequences with a higher degree of similarity. In conclusion, the proposed representation is shown to substantially improve the accuracy of the structural class prediction. A web server that implements the presented prediction method is freely available at http://biomine.ece.ualberta.ca/Structural_Class/SCEC.html.