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.

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Present and Future of Surface-Enhanced Raman Scattering

Ractopamine (RCT) is a beta-adrenergic agonist and its use is forbidden in many countries. With the aim of more sensitive and specific detection of RCT, a RCT structure fragment-based hapten was synthesized by introducing a carboxyl group to octopamine through a reductive amination reaction with ethyl levulinate. Six mice were immunized with a hapten–KLH conjugate, and the best monoclonal antibody (Mab) with an IC50 value of 0.34 ng mL−1 in PBST buffer and 0.41 ng mL−1 in a 10-times diluted swine urine sample was obtained, which had no cross reactivity with clenbuterol and salbutamol. These results demonstrated that a fragment of RCT as a hapten can mimic the antigenicity and specificity of RCT very well, and the Mab has potential applications in the specific monitoring of the illegal use of RCT in real samples.

Fragment-based hapten design and screening of a highly sensitive and specific monoclonal antibody for ractopamine

The polypeptide antibiotics colistin (COL) and bacitracin (Baci) are extensively used as veterinary drugs and feedstock additives in the livestock industry, which inevitably causes residues in animal-origin food, which can accelerate human tolerance to antibiotics. In this study, a portable lateral flow immunoassay (LFIA) for the simultaneous determination of COL and Baci residues in milk was developed. The replacement of gold nanoparticles used in the traditional LFIA with fluorescent microspheres (FMs) to label monoclonal antibodies (mAbs) allowed qualitative and quantitative analyses within a few minutes. Based on the principle of competitive binding to FM-labelled mAbs between analytes in samples and fixed antigens on the membrane, the assay provided qualitative cut-off values of 100 and 50 ng mL-1 for Baci and COL in milk samples. Furthermore, a strip reader-based semi-quantitative detection system could detect lower limits of 7.85 and 1.89 ng mL-1 for Baci and COL, respectively. In conclusion, the proposed multiplex LFIA immunosensor provides an auxiliary analytical tool for the rapid and simultaneous screening of COL and Baci in large cohorts of samples.

A portable fluorescent microsphere-based lateral flow immunosensor for the simultaneous detection of colistin and bacitracin in milk

Medroxyprogesterone (MP) is an anabolic steroid, and its use is forbidden in livestock production. To enforce this ban, it is necessary to develop a highly specific and accurate enzyme-linked immunosorbent assay (ELISA) to detect MP residue. Herein, we describe the first synthesis of a specific hapten which retains the specific structure of MP by replacing the hydroxy group of MP with bromoacetic acid. This MP hapten was conjugated with bovine serum albumin and used as the immunogen in ELISA. The monoclonal antibody was produced by cell fusion. An indirect competitive ELISA was developed based on the monoclonal antibody for the detection of MP, which had a half inhibition concentration of 0.06 ng/mL and a limit of detection of 0.01 ng/mL. No cross-reactivity was found with eight analogous compounds by this method, which showed high specificity for MP. Recoveries ranged from 81 to 88 %, indicating the suitability of this ELISA for MP analysis in food samples.

An Ultrasensitive ELISA for Medroxyprogesterone Residues in Fish Tissues Based on a Structure-Specific Hapten

A rapid and simple immunochromatography method based on a gold nanoparticle-labeled monoclonal antibody was developed for the on-site detection of copper (Cu) in water samples. This monoclonal antibody, obtained by a cell fusion technique, recognized the Cu-ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) complex, but not metal-free EDTA, with high sensitivity and specificity. In optimized conditions, the visual limit of detection for qualitative detection of Cu(II) ions was 10 ng/mL and the LOD for semi-quantitative detection decreased to 0.45 ng/mL with the help of a scanning reader system. The detection process was achieved within 10 min with no cross-reactivity from other heavy metal ions. The recovery of the test samples ranged from 98% to 109%. To our knowledge, this antibody-based test strip for Cu(II) ions has not been previously reported. Based on the above results, this strip sensor could be used as an alternative tool for screening heavy metal pollution in the environment.

Visual Sensor for the Detection of Trace Cu(II) Ions using an Immunochromatographic Strip

A sensitive monoclonal antibody for targeting pentachlorophenol was prepared with an immunization procedure and cell fusion. The antibody was characterized with an indirect competitive enzyme-linked immunosorbent assay (ELISA), which had an IC50 of 0.2 ng/ml for pentachlorophenol under optimized conditions. The cross-reactivity of the ELISA to related compounds was very low. The recovery of pentachlorophenol was 99.2–105% in water samples and 89–110.9% in fish samples. A simple, rapid, and sensitive immunochromatographic strip was produced based on the monoclonal antibody, with a qualitative visual limit of detection of 2 ng/ml in water samples and 10 ng/ml in fish samples, indicating its potential utility in monitoring pentachlorophenol in the field.

https://www.tandfonline.com/doi/pdf/10.1080/09540105.2016.1148668

Chuanlai Xu

Papers

Fragment-based hapten design and screening of a highly sensitive and specific monoclonal antibody for ractopamine

A portable fluorescent microsphere-based lateral flow immunosensor for the simultaneous detection of colistin and bacitracin in milk

An Ultrasensitive ELISA for Medroxyprogesterone Residues in Fish Tissues Based on a Structure-Specific Hapten

Visual Sensor for the Detection of Trace Cu(II) Ions using an Immunochromatographic Strip

Development of a highly sensitive ELISA and immunochromatographic strip to detect pentachlorophenol