Free Boundary Minimal Surfaces in the Unit Three-Ball via Desingularization of the Critical Catenoid and the Equatorial Disk

We construct a new family of high genus examples of free boundary minimal surfaces in the Euclidean unit 3-ball by desingularizing the intersection of a coaxial pair of a critical catenoid and an equatorial disk. The surfaces are constructed by singular perturbation methods and have three boundary components. They are the free boundary analogue of the Costa-Hoffman-Meeks surfaces and the surfaces constructed by Kapouleas by desingularizing coaxial catenoids and planes. It is plausible that the minimal surfaces we constructed here are the same as the ones obtained recently by Ketover using the min-max method.Comment: 45 pages, 10 figure

Li H, Mishra M, Ding S, Miyamoto MM (2018) Diversity and dynamics of “Candidatus Endobugula” and other symbiotic bacteria in Chinese populations of the bryozoan, Bugula neritina. Microb Ecol: in press

The metagenomics datasets for the geographic and life cycle samples of Li et al. (2018) are presented here in four separate folders: (OR_GEO) original reads for the geographic samples; (FFS_GEO) final filtered sequences for the geographic samples; (OR_LC) original reads for the life cycle samples; and (FFS_LC) final filtered sequences for the life cycle samples. Each separate dataset is labelled with the abbreviation of its sample (see Table 2 and Figure 1 of Li et al., 2018) followed by either “OR” or “FFS” (for original reads or final filtered sequences, respectively). For example, the “SY3_OR” dataset includes the original reads for the SY₃ geographic sample, whereas the “S6_FFS” dataset contains the final filtered sequences for the S6 life cycle collection

Peptide Self-Assembly on Mica under Ethanol-Containing Atmospheres: Effects of Ethanol on Epitaxial Growth of Peptide Nanofilaments

Our previous study has shown that the self-assembly of several neurodegenerative-disease-related peptides in ambient water nanofilm condensed on mica is very sensitive to the amount of water on the surface. In this paper, we will demonstrate our hypothesis that the introduction of ethanol into the water nanofilm alters the properties of the interfacial water, resulting in changes of the peptide nanostructures self-assembled on the substrate. The assembly behaviors of peptides under different ethanol-containing atmospheres on mica were investigated by atomic force microscopy. GAV-9a began to form bent nanofilaments under an ethanol-containing atmosphere, and the self-assembled nanofilaments became thicker when a higher ratio of ethanol to water in the vapor was used. Based on these results, we propose a possible mechanism that the peptides adopt a “tilted upright” orientation when ethanol is present in the incubation environment. The effect of the peptide’s terminal groups on the self-assembled nanostructures under the ethanol-containing atmosphere was also discussed

A Universal, Rapid Method for Clean Transfer of Nanostructures onto Various Substrates

Transfer and integration of nanostructures onto target substrates is the prerequisite for their fundamental studies and practical applications. Conventional transfer techniques that involve stamping, lift-off, and/or striping suffer from the process-specific drawbacks, such as the requirement for chemical etchant or high-temperature annealing and the introduction of surface discontinuities and/or contaminations that can greatly hinder the properties and functions of the transferred materials. Herein, we report a universal and rapid transfer method implementable at mild conditions. Nanostructures with various dimensionalities (<i>i.e.</i>, nanoparticles, nanowires, and nanosheets) and surface properties (<i>i.e.</i>, hydrophilic and hydrophobic) can be easily transferred to diverse substrates including hydrophilic, hydrophobic, and flexible surfaces with good fidelity. Importantly, our method ensures the rapid and clean transfer of two-dimensional materials and allows for the facile fabrication of vertical heterostructures with various compositions used for electronic devices. We believe that our method can facilitate the development of nanoelectronics by accelerating the clean transfer and integration of low-dimensional materials into multidimensional structures

Single-Layer MoS₂‑Based Nanoprobes for Homogeneous Detection of Biomolecules

A single-layer MoS₂ nanosheet exhibits high fluorescence quenching ability and different affinity toward ssDNA versus dsDNA. As a proof of concept, the MoS₂ nanosheet has been successfully used as a sensing platform for the detection of DNA and small molecules

Resonance Raman Study of an Anion Channelrhodopsin: Effects of Mutations near the Retinylidene Schiff Base

Optogenetics relies on the expression of specific microbial rhodopsins in the neuronal plasma membrane. Most notably, this includes channelrhodopsins, which when heterologously expressed in neurons function as light-gated cation channels. Recently, a new class of microbial rhodopsins, termed anion channel rhodopsins (ACRs), has been discovered. These proteins function as efficient light-activated channels strictly selective for anions. They exclude the flow of protons and other cations and cause hyperpolarization of the membrane potential in neurons by allowing the inward flow of chloride ions. In this study, confocal near-infrared resonance Raman spectroscopy (RRS) along with hydrogen/deuterium exchange, retinal analogue substitution, and site-directed mutagenesis were used to study the retinal structure as well as its interactions with the protein in the unphotolyzed state of an ACR from <i>Guillardia theta</i> (<i>Gt</i>ACR1). These measurements reveal that (i) the retinal chromophore exists as an all-<i>trans</i> configuration with a protonated Schiff base (PSB) very similar to that of bacteriorhodopsin (BR), (ii) the chromophore RRS spectrum is insensitive to changes in pH from 3 to 11, whereas above this pH the Schiff base (SB) is deprotonated, (iii) when Ser97, the homologue to Asp85 in BR, is replaced with a Glu, it remains in a neutral form (i.e., as a carboxylic acid) but is deprotonated at higher pH to form a blue-shifted species, (iv) Asp234, the homologue of the protonated retinylidene SB counterion Asp212 in BR, does not serve as the primary counteranion for the protonated SB, and (v) substitution of Glu68 with an Gln increases the pH at which SB deprotonation is observed. These results suggest that Glu68 and Asp234 located near the SB exist in a neutral state in unphotolyzed <i>Gt</i>ACR1 and indicate that other unidentified negative charges stabilize the protonated state of the <i>Gt</i>ACR1 SB

Metallaphotoredox-Enabled Construction of the P(O)–N Bond from Aromatic Amines and P(O)–H Compounds

We have developed a dual copper/photoredox-catalyzed approach for the construction of the P(O)–N bond from commercially available aromatic amines and P(O)–H compounds. This metallaphotoredox method avoids toxic or corrosive reagents and does not require prefunctionalized substrates. The reaction has a broad substrate scope and is suitable for the synthesis of phosphonamides and phosphinamides, thus complementing the previous nonphotochemical approaches. The reaction is amenable to the direct modification of drug molecules and can be conducted on a gram scale

Surface-Enhanced Raman Scattering of Ag–Au Nanodisk Heterodimers

We report the fabrication of Ag–Au nanodisk heterodimers based on the modified on-wire lithography method and study their surface-enhanced Raman scattering (SERS) properties experimentally and theoretically. The effects of disk thickness and gap size on SERS are explored. The SERS properties of the optimized heterodimers are compared with those of the respective homodimers and single nanodisks excited at 633 and 488 nm. We found that the enhancement factor (EF) of Ag–Au heterodimers is greater at 633 nm than that at 488 nm, while their EF is between those of the Ag–Ag and Au–Au homodimers. At 488 nm excitation, the calculation indicates that the plasmon energy can be transferred from the Ag disk to the Au disk

Investigation of MoS₂ and Graphene Nanosheets by Magnetic Force Microscopy

For the first time, magnetic force microscopy (MFM) is used to characterize the mechanically exfoliated single- and few-layer MoS₂ and graphene nanosheets. By analysis of the phase and amplitude shifts, the magnetic response of MoS₂ and graphene nanosheets exhibits the dependence on their layer number. However, the solution-processed single-layer MoS₂ nanosheet shows the reverse magnetic signal to the mechanically exfoliated one, and the graphene oxide nanosheet has not shown any detectable magnetic signal. Importantly, graphene and MoS₂ flakes become nonmagnetic when they exceed a certain thickness

Retinal Chromophore Structure and Schiff Base Interactions in Red-Shifted Channelrhodopsin‑1 from <i>Chlamydomonas augustae</i>

Channelrhodopsins (ChRs), which form a distinct branch of the microbial rhodopsin family, control phototaxis in green algae. Because ChRs can be expressed and function in neuronal membranes as light-gated cation channels, they have rapidly become an important optogenetic tool in neurobiology. While channelrhodopsin-2 from the unicellular alga <i>Chlamydomonas reinhardtii</i> (<i>Cr</i>ChR2) is the most commonly used and extensively studied optogenetic ChR, little is known about the properties of the diverse group of other ChRs. In this study, near-infrared confocal resonance Raman spectroscopy along with hydrogen–deuterium exchange and site-directed mutagenesis were used to study the structure of red-shifted ChR1 from <i>Chlamydomonas augustae</i> (<i>Ca</i>ChR1). These measurements reveal that (i) <i>Ca</i>ChR1 has an all-<i>trans</i>-retinal structure similar to those of the light-driven proton pump bacteriorhodopsin (BR) and sensory rhodopsin II but different from that of the mixed retinal composition of <i>Cr</i>ChR2, (ii) lowering the pH from 7 to 2 or substituting neutral residues for Glu169 or Asp299 does not significantly shift the ethylenic stretch frequency more than 1–2 cm^–1 in contrast to BR in which a downshift of 7–9 cm^–1 occurs reflecting neutralization of the Asp85 counterion, and (iii) the <i>Ca</i>ChR1 protonated Schiff base (SB) has stronger hydrogen bonding than BR. A model is proposed to explain these results whereby at pH 7 the predominant counterion to the SB is Asp299 (the homologue to Asp212 in BR) while Glu169 (the homologue to Asp85 in BR) exists in a neutral state. We observe an unusual constancy of the resonance Raman spectra over the broad range from pH 9 to 2 and discuss its implications. These results are in accord with recent visible absorption and current measurements of <i>Ca</i>ChR1 [Sineshchekov, O. A., et al. (2013) Intramolecular proton transfer in channelrhodopsins. <i>Biophys. J. 104</i>, 807–817; Li, H., et al. (2014) Role of a helix B lysine residue in the photoactive site in channelrhodopsins. <i>Biophys. J. 106</i>, 1607–1617]