A model for furcate septal increase in a Triassic scleractiniamorph

Triassic corals with septa that branch repeatedly and centripetally are here assigned to a new genus Furcophyllia. Septa of F. septafindens (Volz, 1896), re−described from the Italian Dolomites, are composed of 3–10 blades (“septal brooms”). Distances between adjacent septa and their branches are equal, and the thickness of all blades is approximately the same throughout ontogeny. However, none of the septal brooms show the same branching pattern. Proposed herein is a simple computer model that reproduces septal pattern, similar to that of Furcophyllia, based on a minimal set of rules: (i) uniform coverage of intra−calicular space; (ii) regular bifurcations following some probability; (iii) keeping some minimal distance between septal branches. The elaborate septal pattern of Furcophyllia suggests a distinct organization of the polyp’s soft tissue, especially mesenteries whose appearance in modern corals is associated with insertion of sclerosepta. Hypothesis 1 suggests that mesenterial pairs flanked only “septal brooms” and that septal branches functionally corresponded with septal microarchitecture. Hypothesis 2 suggests that mesenterial pairs developed between all septal branches that functionally correspond with conventional septa. Delicate menianae, which developed on Furcophyllia septal faces (and many other Triassic corals) resemble similar septal microarchitecture of the Recent agariciid Leptoseris fragilis and may be closely related to the suspension feeding strategy of this coral. The furcate septal arrangement in Furcophyllia is unique among Triassic corals, and generally, among Mesozoic and Cenozoic corals. The only analogous corals are Cretaceous aulastraeoporids (e.g., Preverastrea, Paronastraea), Trochoidomeandra, and some Jurassic rhipidogyrids having secondary (apophysal) septal branches. In some Recent caryophylliids (Trochocyathus rhombocolumna, Phacelocyathus flos) primary septa may also split dichotomously and centripetally

Long-range Interactions for the A3\text{}^{3}1u\text{}_{u} and B3\text{}^{3}0u+\text{}_{u}^{+} States of Cd2\text{}_{2} from Line Shape Measurements

We report on very precise measurements of the absorption profile of the 326.1 nm resonance line of cadmium broadened by interactions with the ground state Cd atoms under thermal equilibrium. The experimental red wing profiles, corrected for the Boltzmann factor at different temperatures, are analysed in terms of the long-range potential parameters including dispersion and resonant interactions. The resonant interaction energy constant C$\text{}_{3}$ is calculated to be 2.31×10$\text{}^{-2}$ eV Å$\text{}^{3}$ and the van der Waals constant C$\text{}_{6}$ for difference potentials between the ground state X$\text{}^{1}$0$\text{}_{ }^{+}$g and the excited states B$\text{}^{3}$0$\text{}_{u}^{+}$ and A$\text{}^{3}$1$\text{}_{u}$ of Cd$\text{}_{2}$ derived experimentally are found to be (182.6± 8) eV Å$\text{}^{6}$ and (289±4) eV Å$\text{}^{6}$, respectively. The former is determined for the first time and the latter is considerably corrected in comparison to earlier determination. The van der Waals constant C$\text{}_{6}$ for the ground state of Cd$\text{}_{2}$ is discussed and estimated to be C$\text{}_{6}^{g}$=(247± 40) eV Å$\text{}^{6}$

Long-Range Interactions and the Oscillator Strength for the 11u,10u+\text{}^{1}1_{u}, \text{}^{1}0_{u}^{+} ← X 10g+\text{}^{1}0_{g}^{+} Transitions in Zn2\text{}_{2}

The interaction potentials for Zn$\text{}_{2}$ electronic states $\text{}^{1}1\text{}_{u}$ and $\text{}^{1}0_{u}^{+}$ correlated with (4 $\text{}^{1}P_{1}$+4 $\text{}^{1}S_{0}$) asymptote in the long-range region (10-25) Å and the oscillator strength f for the absorption transition to these states are derived experimentally from a careful analysis of the self-broadened resonance 213.8 nm line of Zn. It is found that although the interatomic interactions at so long distances are dominated by resonance potential of the form C$\text{}_{3}$/R$\text{}^{3}$ resulting in the Lorentzian line shape, the parameter C$\text{}_{3}$ and thus f value significantly decrease with R decreasing. This effect proved to be a linear function of R$\text{}^{-1}$ yielding the oscillator strength for the considered line f$\text{}_{0}$=1.456 $\pm$ 0.010 from $R \rightarrow \infty$ extrapolation. This value seems to be the most accurate experimental result as yet and shows that the best theoretical values for this quantity are overestimated. It is suggested that the long-range behaviour of the potential energy curves observed here for the first time represents the effective potentials including dominating resonance interactions and a possible slight contribution of the dispersion interactions as well as the R-dependent spin-orbit interaction

Prediction of Secondary Ionization of the Phosphate Group in Phosphotyrosine Peptides

A computational approach, based on a continuum molecular electrostatics model, for the calculation of the pK(a) values of secondary ionization of the phosphate group in phenyl phosphate derivatives is described. The method uses the ESP atomic charges of the mono-anionic and di-anionic forms of the ionizable phosphate group, computed with the use of the density functional method, and applies a new concept of the model group, being the reference state for the pK(a) calculations. Both conformational flexibility and tautomeric degrees of freedom are taken into account in the calculations. The method was parameterized using experimentally available pK(a) values of four derivatives of phenyl phosphates, and phosphotyrosine. Subsequently this parameterization was used to predict pK(a) of the phosphate group in a short peptide Gly-Gly-Tyr(P)-Ala, and in a longer peptide consisting of 12 residues, the latter in water, and in a complex with a protein—phospholipase. The agreement between the computed and the experimental pK(a) values is better than ±0.3 pH units for the optimized solute dielectric constant of 11–13. This approach is promising and its extension to other phospho-amino acids is in progress