Hydration of a 2D Supramolecular Assembly: Bitartrate on Cu(110).

Hydration layers play a key role in many technical and biological systems, but our understanding of these structures remains very limited. Here, we investigate the molecular processes driving hydration of a chiral metal-organic surface, bitartrate on Cu(110), which consists of hydrogen-bonded bitartrate rows separated by exposed Cu. Initially water decorates the metal channels, hydrogen bonding to the exposed O ligands that bind bitartrate to Cu, but does not wet the bitartrate rows.

Addicting diverse bacteria to a noncanonical amino acid.

Engineered orthogonal translation systems have greatly enabled the expansion of the genetic code using noncanonical amino acids (NCAAs). However, the impact of NCAAs on organismal evolution remains unclear, in part because it is difficult to force the adoption of new genetic codes in organisms. By reengineering TEM-1 β-lactamase to be dependent on a NCAA, we maintained bacterial NCAA dependence for hundreds of generations without escape.

Tailoring homochirality at surfaces: going beyond molecular handedness.

Chirality can be bestowed upon a surface by the adsorption of molecules and is usually discussed in terms of the molecular handedness. However, the adsorption process often leads to a new manifestation of chirality in the form of the adsorption footprint, which can also be chiral and generate mirror-images in 2-D. Therefore, in describing the chirality of the interface, one must consider both the handedness and the adsorption 'footedness' of the system.

Recognition and ordering at surfaces: the importance of handedness and footedness.

The expression of chirality at surfaces, arising from the adsorption of chiral molecules, is usually discussed in terms of the molecular handedness. However, the adsorption process often leads to a new manifestation of chirality in the form of the adsorption footprint. Therefore, in order to fully define the chirality of the interface we propose that both the handedness and the footedness of the system must be considered.

c(2×2) water-hydroxyl layer on Cu(110): a wetting layer stabilized by Bjerrum defects.

Understanding the composition and stability of mixed water-hydroxyl layers is a key step in describing wetting and how surfaces respond to redox processes. Here we show that, instead of forming a complete hydrogen bonding network, structures containing an excess of water over hydroxyl are stabilized on Cu(110) by forming a distorted hexagonal network of water-hydroxyl trimers containing Bjerrum defects. This arrangement maximizes the number of strong bonds formed by water donation to OH and provides uncoordinated OH groups able to hydrogen bond multilayer water and nucleate growth.

Probing conformers and adsorption footprints at the single-molecule level in a highly organized amino acid assembly of (S)-proline on Cu(110).

Establishing the nanoscale details of organized amino acid assemblies at surfaces is a major challenge in the field of organic-inorganic interfaces. Here, we show that the dense (4 x 2) overlayer of the amino acid, (S)-proline on a Cu(110) surface can be explored at the single-molecule level by scanning tunneling microscopy (STM), reflection absorption infrared spectroscopy (RAIRS), and periodic density functional theory (DFT) calculations. The combination of experiment and theory, allied with the unique structural rigidity of proline, enables the individual conformers and adsorption footprints adopted within the organized assembly to be determined.

A one-dimensional ice structure built from pentagons.

Heterogeneous ice nucleation has a key role in fields as diverse as atmospheric chemistry and biology. Ice nucleation on metal surfaces affords an opportunity to watch this process unfold at the molecular scale on a well-defined, planar interface. A common feature of structural models for such films is that they are built from hexagonal arrangements of molecules.

Relationship between dental arch width and vertical facial morphology in untreated adults.

The objectives of this study were to investigate if a relationship exists between dental arch width and the vertical facial pattern determined by the steepness of the mandibular plane, and to examine the differences in dental arch widths between male and female untreated adults. Lateral cephalograms and dental casts were obtained from 185 untreated Caucasians (92 males, 93 females) between 18 and 68 years of age with no crossbite, minimal crowding, and spacing. The angle of the mandibular plane (MP) to the anterior cranial base (SN) was measured on cephalograms of each patient.