Submarine Volcanism of the Cabo de Gata Magmatic Arc in the Betic-Rif Orogen, SE Spain: Processes and Products

Volcanic eruptions in subaqueous settings have been traditionally characterized by the study of ancient deposits and, more recently, by indirect observation of the sea floor with different geophysical means. Subaqueous volcanism is largely governed by the physical properties of water and the way water interacts with magma. Among the characteristic products of subaqueous volcanism are hyaloclastite breccias of dense clasts and of pumiceous clasts produced by the quench fragmentation of hot magma in effusive eruptions. Pumice breccias driven by fragmentation of magma in explosive eruptions are not infrequent. The Miocene volcanic zone of Cabo de Gata in southeastern Spain provides excellent exposures where to test the current understanding on subaqueous volcanism. In particular, submarine lavas with a coherent core and an outer carapace of vesicular hyaloclastite together with pumice breccias and crystal tuffs of the El Barronal Formation provide clues to understand transient conditions during explosive and effusive eruptions. Debris avalanches deposits are rather common in Cabo de Gata, such as those of the Los Frailes Formation and the Cerro Estorvillas Formation, and help to understand the instability processes of submarine volcanic edifices and the resultant mass flows. Interbedding of volcanic rocks with shallow water sedimentary rocks allows inferring water depth conditions for volcanism and the subsidence history of the volcano-sedimentary basin

Thr-E11 regulates O2 affinity in Cerebratulus lacteus mini-hemoglobin

The mini-hemoglobin from Cerebratulus lacteus (CerHb) belongs to a class of globins containing the polar Tyr-B10/Gln-E7 amino acid pair that normally causes low rates of O2 dissociation and ultra-high O2 affinity, which suggest O2 sensing or NO scavenging functions. CerHb, however, has high rates of O2 dissociation (kO2 about 200\u2013600 s-1) and moderate O2 affinity (KO2 about 1 microM-1) as a result of a third polar amino acid in its active site, Thr- E11. When Thr-E11 is replaced by Val, kO2 decreases 1000-fold and KO2 increases 130-fold at pH 7.0, 20 \ub0C. The mutation also shifts the stretching frequencies of both heme-bound and photodissociated CO, indicating marked changes of the electrostatic field at the active site. The crystal structure of Thr-E11 3 Val CerHbO2 at 1.70 \uc5 resolution is almost identical to that of the wildtype protein (root mean square deviation of 0.12 \uc5). The dramatic functional and spectral effects of the Thr- E11 3 Val mutation are due exclusively to changes in the hydrogen bonding network in the active site. Replacing Thr-E11 with Val \u201cfrees\u201d the Tyr-B10 hydroxyl group to rotate toward and donate a strong hydrogen bond to the heme-bound ligand, causing a selective increase in O2 affinity, a decrease of the rate coefficient for O2 dissociation, a 40 cm-1 decrease in CO of hemebound CO, and an increase in ligand migration toward more remote intermediate sites