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We report here the discovery of a new form of spontaneously polarized material. Examples of this material, in the form of films, demonstrate the property that they spontaneously harbour electric fields which may exceed 10(8) Vm(-1), achieving potentials of tens of volts on the film surface. The molecules presently identified form a diverse group, thus far of six species, with gas phase dipoles lying between 0.08 D and 0.5 D: propane (0.08 D), isopentane (0.13 D), nitrous oxide (0.167 D), isoprene (0.25 D), toluene (0.385 D) and CF(3)Cl (Freon-13; 0.5 D). Here we concentrate on an understanding of the nature of the interactions which give rise to the spontaneously polarized state, using the measured temperature dependence of the electric field in N(2)O as a diagnostic. We show that the polarized state can arise through a mechanism of non-linear dipole alignment in a single domain in which dipole alignment generates the electric field within the film and the field generates dipole alignment. Non-local interactions take place over the dimension of the thickness of the film and permeate the entire medium through the agency of the electric field. This new type of material may have wide ranging applications in devices and in nanotechnology.

Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nucleic acids and proteins are composed of chiral monomers that show identical stereochemical configuration. Naturally occurring proteins are made up of l-amino acids.[1] Hypotheses for the origin of symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which circularly polarized (CP) light induces an enantiomeric excess (ee) in chiral organic molecules. [2][3][4] This model is supported by both the observation of CP light in the star-forming region of Orion [3,5] and the occurrence of l-enantiomer-enriched amino acids in carbonaceous meteorites. [6][7][8] However, the differential absorption of CP light by amino acid enantiomers, which determines the speed and intensity of enantioselective photolysis, is unknown over a large spectral range. Here we show that significant circular dichroic transitions in amino acids can be observed by extending circular dichroism (CD) spectroscopy to the vacuum-ultraviolet (UV) spectral range. a-H amino acids show the same CD magnitude and sign over a large wavelength range. In a given spectral window [9] CP light is therefore capable of inducing enantiomeric excesses of the same handedness into the proteinogenic amino acids we have studied. Absolute asymmetric photochemistry might thus well have triggered the appearance of l-amino acid based life on Earth. Our results demonstrate that enantiomers of "meteoritic" a-methyl amino acids show dichroic absorption with equal magnitude, yet opposite sign to a-H amino acids. Therefore CP light cannot induce l enantiomeric excesses into a-methyl and a-H amino acids as found in meteorites.To explain the cause of symmetry breaking in biomolecules a well-known theory [2-4, 10, 11] proposes that CP interstellar UV radiation-similar to that identified in the starforming region of Orion in the infrared [3,5] -induced enantiomeric excesses into interstellar and circumstellar organic compounds by asymmetric photochemical reactions prior to their deposition on the early Earth. [12] In support of this theory chiral amino acid structures were identified in interstellar ice analogues [13] and a large number of l-enantiomer-enriched amino acids have been identified in the interior of the Murchison [6] and Murray [7] carbonaceous meteorites.[8] To verify the absolute asymmetric photochemistry model the differential CP-light absorption of proteinogenic and meteoritic amino acid enantiomers requires systematic examination.Until now, the popular and extensively used technique of CD spectroscopy has been used to record electronic CD for chiral molecules in aqueous solution above 190 nm.[14] Water absorbs photons of l < 190 nm, making the vacuum-UV region inaccessible for CD spectroscopy in aqueous solution. By using a synchrotron radiation source for CP light and preparing isotropic amorphous solid-state samples immobilized on MgF 2 windows, we have extended electronic CD measurements to the vacuum-UV spectral range.We observed...

Circular dichroism (CD) spectroscopy is a highly sensitive but low-resolution technique to study the structure of proteins. Combined with molecular modeling or other complementary techniques, CD spectroscopy can provide essential information at higher resolution. To this end, we introduce a new computational method to calculate the electronic circular dichroism spectra of proteins from a structural model or ensemble using the average secondary structure composition and a precalculated set of basis spectra. The method is designed for model validation to estimate the error of a given protein structural model based on the measured CD spectrum. We compared the predictive power of our method to that of existing algorithms, namely, DichroCalc and PDB2CD, and found that it predicts CD spectra more accurately.Our results indicate that the derived basis sets are robust to both experimental errors in the reference spectra and the choice of the secondary structure classification algorithm. For over 80% of the globular reference proteins, our basis sets accurately predict the experimental spectrum solely from their secondary structure composition. For the remaining 20%, correcting for intensity normalization considerably improves the prediction power. Additionally, we show that the predictions for short peptides and an example complex of intrinsically disordered proteins strongly benefit from accounting for side-chain contributions and structural flexibility.

We present the first high resolution vacuum ultraviolet photoabsorption study of amorphous benzene with comparisons to annealed crystalline benzene and the gas phase. Vapour deposited benzene layers were grown at 25 K and annealed to 90 K under conditions pertinent to interstellar icy dust grains and icy planetary bodies in our solar system. Three singlet-singlet electronic transitions in solid benzene correspond to the B, B and E states, redshifted by 0.05, 0.25 and 0.51 eV respectively with respect to the gas phase. The symmetry forbidden B ← A and B ← A transitions exhibit vibronic structure due to vibronic coupling and intensity borrowing from the allowed E ← A transition. Additionally the B ← A structure shows evidence of coupling between intramolecular vibrational and intermolecular lattice modes in crystalline benzene with Davydov crystal field splitting observed. The optically forbidden 0-0 electronic origin is clearly visible as a doublet at 4.69/4.70 eV in the crystalline solid and as a weak broadened feature at 4.67 eV in amorphous benzene. In the case of the B ← A transition the forbidden 0-0 electronic origin is only observed in crystalline benzene as an exciton peak at 5.77 eV. Thicker amorphous benzene samples show diffuse bands around 4.3, 5.0 and 5.4 eV that we tentatively assign to spin forbidden singlet-triplet B ← A, E ← A and B ← A transitions respectively, not previously reported in photoabsorption spectra of amorphous benzene. Furthermore, our results show clear evidence of non-wetting or 'islanding' of amorphous benzene, characterised by thickness-dependent Rayleigh scattering tails at wavelengths greater than 220 nm. These results have significant implications for our understanding of the physical and chemical properties and processes in astrochemical ices and highlight the importance of VUV spectroscopy.

A recent publication described a new group of spontaneously polarized materials in which electric fields in excess of 10(8) V m(-1) may be present. This phenomenon arises through dipole alignment in solid films formed by straightforward deposition from vapour and characterises a novel class of materials. Here we present further results for the properties of these materials, focusing on films of cis-methyl formate. These films are shown to display some notable new chemical physics. We find the novel result that the degree of dipole alignment and the corresponding electric field in films of cis-methyl formate can have a counter-intuitive temperature dependence, increasing six-fold between 80 K and 89 K, in sharp contrast to the pronounced and expected fall with deposition temperature seen both here between 50 K and 75 K and in numerous other species. A theoretical model demonstrates that the switch of gradient with rising temperature should be a general phenomenon and is associated with crossing of a singularity in the gradient occurring at a set of critical values of temperature and alignment.