dance proteins have less sticky surfaces. We also find that stickiness constrains protein evolution, whereby residues in sticky surface patches are more conserved than those found in nonsticky patches. Finally, we find that the constraint imposed by stickiness on protein divergence is proportional to protein abundance, which provides mechanistic insights into the correlation between protein conserva- tion and protein abundance. Overall, the avoidance of nonfunctional interactions significantly influences the physico-chemical and evolu- tionary properties of proteins. Remarkably, the effects observed are consistently larger in E. coli and S. cerevisiae than in H. sapiens, suggesting that promiscuous protein-protein interactions may be freer to accumulate in the human lineage.

https://www.pnas.org/content/pnas/109/50/20461.full.pdf

Cellular crowding imposes global constraints on the chemistry and evolution of proteomes

Results are reported from ab initio theoretical calculations of the structure and energetics of tetrahedral N4. The theoretical basis and implementation of the computations are reviewed, and the results are presented in tables. It is found that a tetrahedral N4 molecule has energy 186 kcal/mole greater than that of two N2 molecules, with a 61-kcal/mole barrier between the two species. Brief consideration is given to the possible use of N4 (should a process for synthesizing it be developed) as a high-energy-density fuel for supersonic transport aircraft.

Theoretical characterization of tetrahedral N4

Two step reversible redox systems of the weitz type

Two hundred years of research have produced only a handful of synthesized all-nitrogen molecules and ions but a lot of stable N n candidates are waiting to be detected. Experimentally, besides the long-known neutrals N2 and linear-N3 there are recent reports of N4 and cyclic-N3 production. In the ions, and have been reported. Ongoing theoretical work has predicted species like N4, N6, N8, N10 and even N60 to be stable. We review the work that has been done recently in this area in both experiment and theory. ContentsPAGE1. Introduction5282. Trinitrogen (N3)5293. Trinitrogen5344. Pentanitrogen5365. Hexanitrogen5396. Heptanitrogen5417. Octanitrogen5418. Polynitrogen compounds with more than eight nitrogens544 8.1 N9 544 8.2 N10 544 8.3 N11 545 8.4 N12 545 8.5 N13−N15 546 8.6 N20−N36 546 8.7 N60 5479. Conclusions548References549

All-nitrogen chemistry: how far are we from N60?

The energies and structures of the 28-electron tetraatomic molecules, composed of the first row nonmetallic elements:  N4 (1), CN2O (2), BFN2 (3), C2O2 (4), B2F2 (5), CBFO (6), C2FN (7), and BNO2 (8) have been studied uniformly by ab initio methods including coupled-cluster theory. New estimates of the stability of the N4 isomers, tetraazatetrahedrane and tetraazacyclobutadiene, are presented, and a new triplet NNNN open-chain isomer has been established computationally. Potential energy surfaces of the nonpolar 1 and the polar 2 are compared. Three-membered cyclic C2v fluorodiazaboririne has been found to be the most stable isomer similar to diazirinone (Chem. Phys. Lett. 1994, 227, 312). Linear triplet CO and BF dimers, OCCO, FBBF, and OCBF, are the most stable forms of 4, 5, and 6, respectively. The singlet cyanofluoromethylene, NCCF, the global energy minimum of 7, is 7 kcal/mol more stable than isomeric CNCF and 10 kcal/mol lower in energy than 3-fluoroazacycloprop-2-ylidene. The singlet and triplet ...

The 28-Electron Tetraatomic Molecules: N4, CN2O, BFN2, C2O2, B2F2, CBFO, C2FN, and BNO2. Challenges for Computational and Experimental Chemistry

The possibility of the nitrogen molecule forming a stable dimer is investigated. Through ab initio calculations in an extended contracted-gaussian basis, it is demonstrated that N4 in tetrahedral geometry and N3 + in D 3h geometry are local minimum points on their respective internuclear potential energy surfaces. The N4 molecule is considerably higher in energy than two ground-state N2 molecules and some study of the barrier for N4 decomposition has been made. The bond lengths and force constants for the two systems are shown to be similar to their hydrocarbon counterparts, C4H4 and C3H3 +, tetrahedrane and cyclopropenyl cation. Other related systems are discussed as well.

Thomas J. Venanzi

Papers

The N4 molecule and the N3 + ion

Hydrophobicity parameters and the bitter taste of L-amino acids.

Nuclear spin-spin coupling constants of bicyclobutanes

Spiroconjugation involving sulfur 3p atomic orbitals