Structural Diversity of 2D Molecular Self-Assemblies Arising from Carboxyl Groups Attached to a Molecule: An STM Study at the Liquid-Solid Interface

Understanding the molecular self-assembly behavior, especially at the microscopic level, sheds light on the rational design of artificial supramolecular systems at surfaces. In this work, scanning tunneling microscopy (STM) and force field simulations were utilized to explore two molecular systems where two and four carboxyl groups are symmetrically modified onto a skeleton. The two target molecules are 4,4'-(ethyne-1,2-diyl) dibenzoic acid (EBA) and 1,1'-ethynebenzene-3,3',5,5,'-tetracarboxylic acid (TCA). The former molecular assembly led to robust close packing, whereas the latter resulted in low-density arrangements that present significant adaption, namely, undergoing phase transformations upon external stimulations, e.g., sensitive to STM-polarity switching and guest molecule incorporations.

Two-dimensional self-assembly and co-assembly of two tetracarboxylic acid derivatives investigated by STM

In this work, the two-dimensional self-assembly and co-assembly behaviors of two tetracarboxylic acid derivatives (H4BDETP and H4BTB) were investigated by scanning tunneling microscopy (STM). H4BDETP molecules self-assembled into linear nanostructures, and H4BTB molecules formed lamellar and tetragonal nanostructures. The formation of a H4BDETP/H4BTB co-assembly nanostructure was closely related to the deposition sequence of H4BDETP and H4BTB on highly oriented pyrolytic graphite (HOPG). The introduction of H4BTB into the self-assembly system of H4BDETP resulted in the emergence of the H4BDETP/H4BTB nanostructure, while the addition of H4BDETP had no effect on the self-assembly system of H4BTB and a H4BDETP/H4BTB co-assembly nanostructure was not obtained.

Large-scale genome sequencing reveals the driving forces of viruses in microalgal evolution

Being integral primary producers in diverse ecosystems, microalgal genomes could be mined for ecological insights, but representative genome sequences are lacking for many phyla. We cultured and sequenced 107 microalgae species from 11 different phyla indigenous to varied geographies and climates. This collection was used to resolve genomic differences between saltwater and freshwater microalgae. Freshwater species showed domain-centric ontology enrichment for nuclear and nuclear membrane functions, while saltwater species were enriched in organellar and cellular membrane functions. Further, marine species contained significantly more viral families in their genomes (p = 8e-4). Sequences from Chlorovirus, Coccolithovirus, Pandoravirus, Marseillevirus, Tupanvirus, and other viruses were found integrated into the genomes of algal from marine environments. These viral-origin sequences were found to be expressed and code for a wide variety of functions. Together, this study comprehensively defines the expanse of protein-coding and viral elements in microalgal genomes and posits a unified adaptive strategy for algal halotolerance.

A two-dimensional crystal formed by pentamers on Au(111)

A new type of two-dimensional crystal comprising supramolecular pentamers on Au(111) is studied using an ultra-high vacuum low-temperature scanning tunnelling microscope.