There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Gold nanoparticles have been used in biomedical applications since their first colloidal syntheses more than three centuries ago. However, over the past two decades, their beautiful colors and unique electronic properties have also attracted tremendous attention due to their historical applications in art and ancient medicine and current applications in enhanced optoelectronics and photovoltaics. In spite of their modest alchemical beginnings, gold nanoparticles exhibit physical properties that are truly different from both small molecules and bulk materials, as well as from other nanoscale particles. Their unique combination of properties is just beginning to be fully realized in range of medical diagnostic and therapeutic applications. This critical review will provide insights into the design, synthesis, functionalization, and applications of these artificial molecules in biomedicine and discuss their tailored interactions with biological systems to achieve improved patient health. Further, we provide a survey of the rapidly expanding body of literature on this topic and argue that gold nanotechnology-enabled biomedicine is not simply an act of ‘gilding the (nanomedicinal) lily’, but that a new ‘Golden Age’ of biomedical nanotechnology is truly upon us. Moving forward, the most challenging nanoscience ahead of us will be to find new chemical and physical methods of functionalizing gold nanoparticles with compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term term effects on human health and reproduction (472 references).

The golden age: gold nanoparticles for biomedicine

Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

/pdf/present-and-future-of-surface-enhanced-raman-scattering-34aqgcm385.pdf

Present and Future of Surface-Enhanced Raman Scattering

A non-pretreatment monitoring method based on immunochromatographic test (ICT) strips was developed to test for chloramphenicol (CAP) in raw milk. This assay was designed to measure competitive binding affinities for CAP molecules in raw milk and CAP antigen immobilized on strips with colloidal gold nanoparticles (GNPs, average diameter of 30 nm) labeled with anti-CAP monoclonal antibody (CAP mAb). Several working conditions, including the CAP solvent, different types and concentrations of CAP mAb, coating antigen, and GNP, were optimized for performance. After optimization, the detection process was carried out in 8 min with a visual limit of detection (LOD) of 0.3 ng/mL for qualitative detection and a LOD of 0.064 ng/mL for semi-quantitative detection. No cross-reactivity was detected toward CAP analogs. Based on these results, this simple and ultrasensitive assay could be thoroughly applied in the on-site testing of CAP in raw milk.

An ultrasensitive immunochromatographic assay for non-pretreatment monitoring of chloramphenicol in raw milk

Chiral semiconductor nanorods and their heterostructures have attracted intense attention. In this work, it was shown that chiral amino acids on CdSe@CdS semiconductor nanorods (SNR) displayed circular dichroism bands (CD, 200–480 nm). Longer SNRs were found to induce stronger CD intensities, while an increase in the SNR diameter led to a clear CD band redshift. Multi-site post-growth of platinum (Pt) and gold (Au) further enhanced the CD intensity and induced CD band transitions. Electromagnetic calculations revealed that the metal post-growth gave rise to a strong electromagnetic field enhancement, with Pt inducing a stronger enhancement than Au. The optimized chiral multi-sites platinum on SNR displayed higher photocatalytic activities manifested that the deposited metal endowed energy transfer and enhanced the separation of photo-excited electrons and holes. These findings demonstrated that the multi-sites deposited metal provided a method to produce strong optical activity of nanostructures by adjusting the morphology of the semiconductor nanorod.

Chiral semiconductor nanorod heterostructures with high photocatalysis activity

A specific monoclonal antibody against aflatoxin (AF) M1 was prepared by a duo-immunogen immunization strategy. After two immunizations of Balb/c mice with AFB1 keyhole limpet hemocyanin (KLH) conjugates and followed by five subsequent immunizations of AFM–KLH, the mice secreting antibody against AFM1 were selected for cell fusion and a 7C6-H1 cell line was obtained to produce the antibody. The 50% inhibition rate of the prepared antibody was calculated as 0.034 ± 0.002 μg L−1. The anti-AFM1 antibody was characterized with high affinity to AFM1 (1.28 × 109 mol L−1) and low cross-reactivity to related AFs (<5%). With a competitive format, an immunochromatographic strip was developed using AFB1–bovine serum albumin as the immobilized antigen and anti-AFM1 antibody labeled with gold nanoparticles as tracers. Without any sample preparation, the strip could be directly applied to detect AFM1 contamination in liquid milk. The minimum cut-off concentrations were 0.2 μg L−1 and 1.6 μg kg−1 in liquid milk and powdered milk, respectively, by assessment with the naked eye. Detection of real samples and spiked milk samples indicated the potential of this strip in routine AFM1 monitoring.

Immunochromatographic strip development for ultrasensitive analysis of aflatoxin M1

Chirality has been one of the core research topics in the multidisciplinary fields of materials science, chemistry, biology, medicine, and physics. The subject of chirality in nanomaterials represents one of the most dynamic areas, and it has recently emerged as a new “growth point” of nanoscience. Of particular interest, recent advances in chiral materials endow the asymmetry‐breaking capability to synthesize chiral materials with tunable and reconfigurable chiroptical properties, as well as various functions and emerging applications. Breakthroughs and technological developments have led to the study of many interesting properties of chiral nanocrystals, and some have demonstrated realistic potential, and may address key challenges at the heart of physical sciences. It is timely and necessary to organize a special issue to comprehensively review the state‐of‐the‐art development of chiral materials and future research topics.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202005110

Emerging Chiral Materials.

Tylosin (TYL) and tilmicosin (TIM) are macrolide antibiotics, and maximum residue limits (MRLs) have been set to control their illegal usage in food. We developed a sensitive indirect competitive enzyme-linked immunosorbent assay and rapid immunochromatographic strip (ICS) test to simultaneously detect TYL and TIM based on an innovative hapten (TYL-carboxymethoxylamine hemihydrochloride). The monoclonal antibody 2B3 was obtained with the isotype IgG1, and TYL and TIM had half maximal inhibitory concentrations of 0.57 and 2.10 ng/ml, respectively. The cross-reactivity values were 100%, 27.57%, 97.43%, and 62.42% for TYL, TIM, desmycosin, and acetylisovaleryl tylosin, respectively. By optimizing, the standard dilution buffer was based on 0.8% NaCl, pH 7.4 and 5% acetonitrile. The recoveries ranged from 89.37% to 112.00% in the honey samples, which suggests that the assay would be reliable in the analysis of real honey samples. In addition, an ICS was developed for qualitative, semi-quantitative, and...

Chuanlai Xu

Papers

An ultrasensitive immunochromatographic assay for non-pretreatment monitoring of chloramphenicol in raw milk

Chiral semiconductor nanorod heterostructures with high photocatalysis activity

Immunochromatographic strip development for ultrasensitive analysis of aflatoxin M1

Emerging Chiral Materials.

Simultaneous detection of tylosin and tilmicosin in honey using a novel immunoassay and immunochromatographic strip based on an innovative hapten