Long-distance communication can enable collective migration in a dynamic seascape.

Social information is predicted to enhance the quality of animals' migratory decisions in dynamic ecosystems, but the relative benefits of social information in the long-range movements of marine megafauna are unknown. In particular, whether and how migrants use nonlocal information gained through social communication at the large spatial scale of oceanic ecosystems remains unclear. Here we test hypotheses about the cues underlying timing of blue whales' breeding migration in the Northeast Pacific via individual-based models parameterized by empirical behavioral data. Comparing emergent patterns from individual-based models to individual and population-level empirical metrics of migration timing, we find that individual whales likely rely on both personal and social sources of information about forage availability in deciding when to depart from their vast and dynamic foraging habitat and initiate breeding migration. Empirical patterns of migratory phenology can only be reproduced by models in which individuals use long-distance social information about conspecifics' behavioral state, which is known to be encoded in the patterning of their widely propagating songs. Further, social communication improves pre-migration seasonal foraging performance by over 60% relative to asocial movement mechanisms. Our results suggest that long-range communication enhances the perceptual ranges of migrating whales beyond that of any individual, resulting in increased foraging performance and more collective migration timing. These findings indicate the value of nonlocal social information in an oceanic migrant and suggest the importance of long-distance acoustic communication in the collective migration of wide-ranging marine megafauna.

Geometry-Dependent Arrhythmias in Electrically Excitable Tissues.

Little is known about how individual cells sense the macroscopic geometry of their tissue environment. Here, we explore whether long-range electrical signaling can convey information on tissue geometry to individual cells. First, we studied an engineered electrically excitable cell line. Cells grown in patterned islands of different shapes showed remarkably diverse firing patterns under otherwise identical conditions, including regular spiking, period-doubling alternans, and arrhythmic firing. A Hodgkin-Huxley numerical model quantitatively reproduced these effects, showing how the macroscopic geometry affected the single-cell electrophysiology via the influence of gap junction-mediated electrical coupling. Qualitatively similar geometry-dependent dynamics were observed in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes. The cardiac results urge caution in translating observations of arrhythmia in vitro to predictions in vivo, where the tissue geometry is very different. We study how to extrapolate electrophysiological measurements between tissues with different geometries and different gap junction couplings.

Engineering plasmonic nanorod arrays for colon cancer marker detection.

Engineering plasmonic nanomaterials or nanostructures towards ultrasensitive biosensing for disease markers or pathogens is of high importance. Here we demonstrate a systematic approach to tailor effective plasmonic nanorod arrays by combining both comprehensive numerical discrete dipole approximations (DDA) simulation and transmission spectroscopy experiments. The results indicate that 200×50 nm nanorod arrays with 300×500 nm period provide the highest figure of merit (FOM) of 2.4 and a sensitivity of 310 nm/RIU. Furthermore, we demonstrate the use of nanorod arrays for the detection of single nucleotide polymorphism in codon 12 of the K-ras gene that are frequently occurring in early stages of colon cancer, with a sensitivity down to 10 nM in the presence of 100-fold higher concentration of the homozygous genotypes. Our work shows significant potential of nanorod arrays towards point-of-care applications in diagnosis and clinical studies.

Metamaterials-based label-free nanosensor for conformation and affinity biosensing.

Analysis of molecular interaction and conformational dynamics of biomolecules is of paramount importance in understanding their vital functions in complex biological systems, disease detection, and new drug development. Plasmonic biosensors based upon surface plasmon resonance and localized surface plasmon resonance have become the predominant workhorse for detecting accumulated biomass caused by molecular binding events. However, unlike surface-enhanced Raman spectroscopy (SERS), the plasmonic biosensors indeed are not suitable tools to interrogate vibrational signatures of conformational transitions required for biomolecules to interact. Here, we show that highly tunable plasmonic metamaterials can offer two transducing channels for parallel acquisition of optical transmission and sensitive SERS spectra at the biointerface, simultaneously probing the conformational states and binding affinity of biomolecules, e.g., G-quadruplexes, in different environments. We further demonstrate the use of the metamaterials for fingerprinting and detection of the arginine-glycine-glycine domain of nucleolin, a cancer biomarker that specifically binds to a G-quadruplex, with the picomolar sensitivity.

Vertically aligned gold nanorod monolayer on arbitrary substrates: self-assembly and femtomolar detection of food contaminants.

Public attention to the food scandals raises an urgent need to develop effective and reliable methods to detect food contaminants. The current prevailing detections are primarily based upon liquid chromatography, mass spectroscopy, or colorimetric methods, which usually require sophisticated and time-consuming steps or sample preparation. Herein, we develop a facile strategy to assemble the vertically aligned monolayer of Au nanorods with a nominal 0.8 nm gap distance and demonstrate their applications in the rapid detection of plasticizers and melamine contamination at femtomolar level by surface-enhanced Raman scattering spectroscopy (SERS). The SERS signals of plasticizers are sensitive down to 0.9 fM concentrations in orange juices. It is the lowest detection limit reported to date, which is 7 orders of magnitude lower than the standard of United States (6 ppb). The highly organized vertical arrays generate the reproducible "SERS-active sites" and can be achieved on arbitrary substrates, ranging from silicon, gallium nitride, glass to flexible poly(ethylene naphthalate) substrates.

Optimizing Electromagnetic Hotspots in Plasmonic Bowtie Nanoantennae.

Sensitivity is a key factor in the improvement of nanoparticle-based biosensors. Bowtie nanoantennae have shown high sensitivity for both surface-enhanced Raman scattering (SERS)- and localized surface plasmon resonance (LSPR)-based biosensing. In this work, optical bowtie nanoantennae with varying geometries were simulated, fabricated, and characterized. We successfully fabricated sub-5 nm gaps between prisms. The gap between prisms, the prism size, and the radius of curvature of the prism corners were characterized for their effects on the optical and electromagnetic properties. Bowties were characterized using LSPR, SERS, and photochemical near-field imaging. The results indicate that the radius of curvature of the prism corners has an important effect on the SERS abilities of a nanoparticle array. The trends described herein can be utilized to intelligently design highly sensitive SERS and LSPR biosensing substrates.

Estrogen attenuates gp120- and tat1-72-induced oxidative stress and prevents loss of dopamine transporter function.

Postmenopausal women who are infected with HIV are at risk for experiencing dementia and Parkinson's-like symptoms associated with low levels of estrogen. Neurotoxic damage leading to these symptoms may involve HIV-associated proteins gp120 and/or tat(1-72) (tat). Our hypothesis is that 17beta-Estradiol (E(2)) is an effective agent for protection against gp120/tat-induced damage associated with increased oxidative stress, with particular focus on peroxynitrite-induced oxidative stress. We used SK-N-SH cells and striatal synaptosomes from Sprague-Dawley rats as model systems to assess neuroprotection by E(2). Cells coincubated with SIN-1(3-morpholinosydnonimine) or tat and gp120, together or separately, significantly increased oxidative stress on the SK-N-SH cells, as indicated by the increase in the levels of dichlorofluorescein (DCFH) fluorescence. These data suggest that a component of tat and gp120 neurotoxicity may be due to increased oxidative stress. Coincubation with E(2) attenuated tat- and gp120-induced increase in fluorescence. Coincubation with progesterone had no effect on tat-induced fluorescence, whereas coincubation with the E(2) antagonist ICI 182,780 and E(2) completely prevented the effects observed with E(2) alone. Both gp120 and tat decreased [(3)H] dopamine uptake into striatal synaptosomes by decreasing the V(max) of the dopamine transporter (DAT). Pretreatment of synaptosomes with E(2) (100 nM) partially reversed this reduction. In conclusion, E(2) appears to be effective for preventing the oxidative stress and loss of DAT function associated with gp120/tat neurotoxicity.