Peptides are multifunctional reagents (reducing and capping agents) that can be used for the synthesis of biocompatible metal nanoparticles under relatively mild conditions. However, the progress in peptide synthesis of metal nanoparticles has been slow due to the lack of peptide design rules. It is difficult to establish sequence-reactivity relationships from peptides isolated from biological sources (e.g., biomineralizing organisms) or selected by combinatorial display libraries because of their widely varying compositions and structures. The abundance of random and inactive amino acid sequences in the peptides also increases the difficulty in knowledge extraction. In this study, a "bottom-up" approach was used to formulate a set of rudimentary rules for the size- and shape-controlled peptide synthesis of gold nanoparticles from the properties of the 20 natural alpha-amino acids for AuCl(4)(-) reduction and binding to Au(0). It was discovered that the reduction capability of a peptide depends on the presence of certain reducing amino acid residues, whose activity may be regulated by neighboring residues with different Au(0) binding strengths. Another finding is the effect of peptide net charge on the nucleation and growth of the Au nanoparticles. On the basis of these understandings, several multifunctional peptides were designed to synthesize gold nanoparticles in different morphologies (nanospheres and nanoplates) and with sizes tunable by the strategic placement of selected amino acid residues in the peptide sequence. The methodology presented here and the findings are useful for establishing the scientific basis for the rational design of peptides for the synthesis of metal nanostructures.

The recent outbreak of Zika virus (ZIKV) infections in the Americas represents a serious threat to the global public health. The viral protease that processes viral polyproteins during infection appears as an attractive drug target. Here we report a crystal structure at 1.84 Å resolution of ZIKV non-structural protein NS2B-NS3 protease with the last four amino acids of the NS2B cofactor bound at the NS3 active site. This structure represents a post-proteolysis state of the enzyme during viral polyprotein processing and provides insights into peptide substrate recognition by the protease. Nuclear magnetic resonance (NMR) studies and protease activity assays unravel the protein dynamics upon binding the protease inhibitor BPTI in solution and confirm this finding. The structural and functional insights of the ZIKV protease presented here should advance our current understanding of flavivirus replication and accelerate structure-based antiviral drug discovery against ZIKV.

This paper reports a novel synthesis approach of bovine serum albumin (BSA) protein-templated ultrasmall (<2 nm) Ag nanocluster (NC) with strong singlet oxygen generation capacity for photodynamic therapy (PDT). An atomically precise BSA-Ag NC (i.e., 13 Ag atoms per cluster) is successfully synthesized for the first time by using NaOH-dissolved NaBH solution as the controlling reducing agent. The ubiquitous size of BSA-Ag NC results in unique behaviors of its photoexcited states as characterized by the ultrafast laser spectroscopy using time-correlated single photon counting and transient absorption techniques. In particular, triply excited states can be largely present in the excited BSA-Ag NC and readily sensitized molecular oxygen to produce singlet oxygen ( O ) with a high quantum efficiency (≈1.26 using Rose Bengal as a standard). This value is much higher than its Au analogue (i.e., ≈0.07 for BSA-Au NC) and the commonly available photosensitizers. Due to the good cellular uptake and inherent biocompatibility imparted by the surface protein, BSA-Ag NC can be applied as an effective PDT agent in generating O to kill cancer cell as demonstrated in this study.

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A facile, environmentally benign shape-controlled synthesis of anisotropic crystalline gold nanostructures at room temperature has been developed using aspartic acid (Asp) as the reducing, particle-stabilizing, and shape-directing agents. Great latitude in the control of particle size and shape, including formation of hitherto unreported nanoribbons and nanowires, could be accomplished through simple manipulation of the experimental conditions. The gold precursor concentration [HAuCl4] and the concentration ratio of aspartic acid to gold precursor, R ([Asp]/[HAuCl4]), were found to be critical factors in morphosynthesis. Their effects on crystal growth into different final morphologies were examined and correlated with the growth kinetics. The experimental results also suggested a growth mechanism where the difference in rates between reduction of the gold precursor on {111} and {100} family of planes, competition between the reduction and capping functions of Asp, and Asp surface coverage determined the morphology of the nanostructure formed.

Multi-objective control systems for complex robots usually have to handle multiple prioritized tasks. Most existing hierarchical control techniques handle either strict task priorities by using null-space projectors or a sequence of quadratic programs; or non strict task priorities by using a weighting strategy. This paper proposes a novel approach to handle both strict and non-strict priorities of an arbitrary number of tasks. It can achieve multiple priority rearrangements simultaneously. A generalized projector, which makes it possible to completely project a task into the null-space of a set of tasks, while partially projecting it into the null-space of some other tasks, is developed. This projector can be used to perform priority transitions and task insertion or deletion. The control input is computed by solving one quadratic programming problem, where generalized projectors are adopted to maintain a task hierarchy, and equality or inequality constraints can be implemented. The effectiveness of this approach is demonstrated on a simulated robotic manipulator in a dynamic environment.

Metal nanoparticles (NP) that exhibit localized surface plasmon resonance play an important role in metalenhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS). Among the optical biosensors, MEF and SERS stand out to be the most sensitive techniques to detect a wide range of analytes from ions, biomolecules to macromolecules and microorganisms. Particularly, anisotropic metal NPs with strongly enhanced electric field at their sharp corners/edges under a wide range of excitation wavelengths are highly suitable for developing the ultrasensitive plasmonenhanced biosensors. In this review, we first highlight the reliable methods for the synthesis of anisotropic gold NPs and silver NPs in high yield, as well as their alloys and composites with good control of size and shape. It is followed by the discussion of different sensing mechanisms and recent advances in the MEF and SERS biosensor designs. This includes the review of surface functionalization, bioconjugation and (directed/self) assembly methods as well as the selection/screening of specific biorecognition elements such as aptamers or antibodies for the highly selective biodetection. The right combinations of metal nanoparticles, biorecognition element and assay design will lead to the successful development of MEF and SERS biosensors targeting different analytes both in-vitro and in-vivo. Finally, the prospects and challenges of metal-enhanced biosensors for future nanomedicine in achieving ultrasensitive and fast medical diagnostics, high-throughput drug discovery as well as effective and reliable theranostic treatment are discussed.