The cyclic lipodepsipeptide, syringomycin E, when incorporated into planar lipid bilayer membranes, forms two types of channels (small and large) that are different in conductance by a factor of sixfold. To discriminate between a cluster organization-type channel structure and other possible different structures for the two channel types, their ionic selectivity and pore size were determined. Pore size was assessed using water-soluble polymers. Ion selectivity was found to be essentially the same for both the small and large channels. Their reversal (zero current) potentials with the sign corresponding to anionic selectivity did not differ by more than 3 mV at a twofold electrolyte gradient across the bilayer. Reduction in the single-channel conductance induced by poly(ethylene glycol)s of different molecular weights demonstrated that the aqueous pore sizes of the small and large channels did not differ by more than 2% and were close to 1 nm. Based on their virtually identical selectivity and size, we conclude that large syringomycin E channels are clusters of small ones exhibiting synchronous opening and closing.

Using the planar lipid bilayer technique we demonstrate that the lipodepsipeptide antibiotic, syringomycin E, forms voltage-sensitive ion channels of weak anion selectivity. The formation of channels in bilayers made from dioleoylglycerophosphatidylserine doped with syringomycin E at one side (1-40 micrograms/ml) was greatly affected by cis-positive voltage. A change of voltage from a positive to a negative value resulted in (i) an abrupt increase in the single channel conductance (the rate of increase was voltage dependent) simultaneous with (ii) a closing of these channels and an exponential decrease in macroscopic conductance over time. The strong voltage dependence of multichannel steady state conductance, the single channel conductance, the rate of opening of channels at positive voltages and closing them at negative voltages, as well as the observed abrupt increase of single channel conductance after voltage sign reversal suggest that the change of the transmembrane field induces a significant rearrangement of syringomycin E channels, including a change in the spacing of charged groups that function as voltage sensors. The conductance induced by syringomycin E increased with the sixth power of syringomycin E concentration suggesting that at least six monomers are required for channel formation.

Abstract. We present the essential dynmnic model of the •nesospheric photochemical system (PCS) •'md suggest a step-by-step procedure for elaborating such a model of an arbitrary atmospheric PCS. The model demonstrates the same possibilities of nonlinear dynamic behavior and qualitatively the same dynamic characteristics as the corresponding original model, but is much simpler than the latter. We show the adequacy of the essential model compared with the original one in bifurcation diagrams, equilibrimn states, and such new characteristics as correlation dimension and minirotan embedding dimension of a chaotic attractor. The model can be used both for identi•ing and studying the mechanisms of the nonlinear dynmnic behavior of the mesaspheric PCS, as well as for solving a number of problems aimed at revealing nonlinear photochemical phenomena in the actual mesasphere.

Abstract. The methods of nonlinear dynamics are used to reveal the origin of complicated dynamic behaviour (CDB) of a dynamic model of the mesospheric photochemical system (PCS) perturbed by diurnal variations in photolysis rates. We found that CDB appearance during the multi-day evolution is unambiguously determined by two peculiarities in the model behaviour during its 24-hours evolution. These peculiarities are the presence of a stage of abrupt changes in reagent concentrations and the "humped" dependence of the end-night atomic hydrogen concentrations on those at the beginning of the night. Using a successive analysis we found that these two peculiarities are, in turn, conditioned by the specific features of the chemical processes involved in the model, namely, by the catalytic cycle whose net rate is independent of the concentration of the destroyed species (here, it is atomic oxygen). We believe that similar peculiarities inherent in other atmospheric PCSs indicate that under appropriate conditions they may also demonstrate CDB. We identified the mechanism of the CDB appearance and described it in two ways. The first one reveals a sequence of the processes causing the exponential (on the average) growth of a perturbation of the solution with time. In particular, we found that the behaviour of small perturbations of an arbitrary solution of model equations is identical to the behaviour of a linear oscillator excited parametrically. The second way shows the mechanism of CDB appearance by means of 1-dimensional mapping, which is, basically, the same as the well-known Feigenbaum mappings.

Recent experiments on the UV and electron beam irradiation of solid O 2 reveals a series of IR features near the valence antisymmetric vibration band of O 3 which are frequently interpreted as the formation of unusual O n allotropes in the forms of weak complexes or covalently bound molecules. In order to elucidate the question of the nature of the irradiation products, the structure, relative energies, and vibrational frequencies of various forms of O n (n = 1−6) in the singlet, triplet, and, in some cases, quintet states were studied using the CCSD(T) method up to the CCSD(T,full)/cc-pCVTZ and CCSD(T,FC)/aug-cc-pVTZ levels. The results of calculations demonstrate the existence of stable highly symmetric structures O 4 (D 3h ), O 4 (D 2d ), and O 6 (D 3d ) as well as the intermolecular complexes O 2 ·O 2 , O 2 ·O 3 , and O 3 ·O 3 in different conformations. The calculations show that the local minimum corresponding to the O 3 ···O complex is quite shallow and cannot explain the ν 3 band features close to 1040 cm −1 , as was proposed previously. For the ozone dimer, a new conformer was found which is more stable than the structure known to date. The effect of the ozone dimer on the registered IR spectra is discussed.