Reactions between Zinc Metallothionein and Carbonic Anhydrase

More than 25% of proteins require metal ion cofactors for structure or function. The interactions between metalloproteins have largely been overlooked, though these interactions ultimately govern metal localization and control metal ion homeostasis. Mammalian metallothionein (MT) is a small, cysteine-rich metalloprotein that binds numerous metal ions per protein strand. Up to seven divalent metals, such as zinc or cadmium, are wrapped into a clustered two-domain structure. This unusually high metal content places MT as an attractive candidate for studying interactions with other metal-binding proteins. This present study investigates the metal transfer reactions between MTs and other metalloproteins, using carbonic anhydrase (CA) as a putative zinc-dependent enzyme. This thesis presents electrospray ionization mass spectrometric (ESI-MS) data showing the competitive zinc metallation reactions between apoCA and various apoMTs. Modelling of the ESI-MS data is used to determine the reaction parameters and those parameters are shown to be reflected directly in the raw data. These results demonstrate how MT can act as a homeostatic buffer of metal ions, by binding them with different affinities. The kinetics of the metal transfers between zinc MTs and cadmium or zinc CA show that the rates of metal transfer between the two metalloproteins is directly dependent on the metal content of the MT. Further studies on the domain specific properties of MT using shortened MT domain fragment proteins show that: (i) there is no significant degree of domain specificity in metal binding to apoMTs; (ii) the weakest bound metal ion is located within the N-terminal domain of the intact MT protein; (iii) the highest affinity binding site is located within the C-terminal domain; and, (iv) domain-domain interactions within the MT peptide strand modulate metal binding affinities. Taken together, these results support the homeostatic roles of metallothionein proteins while also challenging the mechanisms for metal binding and release to apoenzymes

Diurnal patterns of wheat spectral reflectances and their importance in the assessment of canopy parameters from remotely sensed observations

Spectral reflectances of Produra wheat were measured at 13 different times of the day at Phoenix, Arizona, during April 1979 using a nadir-oriented hand-held 4-band radiometer which had bandpass characteristics similar to those on LANDSAT satellites. Different Sun altitude and azimuth angles caused significant diurnal changes in radiant return in both visible and near-IR regions of the spectrum and in several vegetation indices derived from them. The magnitude of these changes were related to different canopy architecture, percent cover and green leaf area conditions. Spectral measurements taken at each time period were well correlated with green leaf area index but the nature of the relationship changed significantly with time of day. Thus, a significant bias in the estimation of the green leaf area index from remotely sensed spectral data could occur if sun angles are not properly accounted for

Hand-held radiometry: A set of notes developed for use at the Workshop of Hand-held radiometry

A set of notes was developed to aid the beginner in hand-held radiometry. The electromagnetic spectrum is reviewed, and pertinent terms are defined. View areas of multiband radiometers are developed to show the areas of coincidence of adjacent bands. The amounts of plant cover seen by radiometers having different fields of view are described. Vegetation indices are derived and discussed. Response functions of several radiometers are shown and applied to spectrometer data taken over 12 wheat plots, to provide a comparison of instruments and bands within and among instruments. The calculation of solar time is reviewed and applied to the calculation of the local time of LANDSAT satellite overpasses for any particular location in the Northern Hemisphere. The use and misuse of hand-held infrared thermometers are discussed, and a procedure for photographic determination of plant cover is described. Some suggestions are offered concerning procedures to be followed when collecting hand-held spectral and thermal data. A list of references pertinent to hand-held radiometry is included

Dissipative instability in a partially ionised prominence plasma slab

We investigate the nature of dissipative instability appearing in a prominence planar thread filled with partially ionised plasma in the incompressible limit. The importance of partial ionisation is investigated in terms of the ionisation factor and wavelength of waves propagating in the slab. To highlight the role of partial ionisation, we have constructed models describing various situations we can meet in solar prominence fine structure. Matching the solutions for the transversal component of the velocity and total pressure at the interfaces between the prominence slab and surrounding plasmas, we derived a dispersion relation whose imaginary part describes the evolution of the instability. Results are obtained in the limit of weak dissipation. We have investigated the appearance of instabilities in prominence dark plumes using single and two-fluid approximations. We show that dissipative instabilities appear for flow speeds that are less than the Kelvin-Helmholtz instability threshold. The onset of instability is determined by the equilibrium flow strength, the ionisation factor of the plasma, the wavelength of waves and the ion-neutral collisional rate. For a given wavelength and for ionisation degrees closer to a neutral gas, the propagating waves become unstable for a narrow band of flow speeds, meaning that neutrals have a stabilising effect. Our results show that the partially ionised plasma describing prominence dark plumes becomes unstable only in a two-fluid (charged particles-neutrals) model, that is for periods that are smaller than the ion-neutral collision time. The present study improves our understanding of stability of solar prominences and the role of partial ionisation in destabilising the plasma. We show the necessity of two-fluid approximation when discussing the nature of instabilities: waves in a single fluid approximation show a great deal of stability.Comment: 12 pages, 11 figure

Eliokarmos humanii (Hyacinthaceae, Ornithogaloideae), a new species from Namaqualand in South Africa and a new combination in the genus

A new species of the southern Africa endemic genus Eliokarmos, that includes the well-known chincherinchees, is described from the vicinity of Kotzesrus, Northern Cape Province of South Africa. Eliokarmos humanii sp. nov. is unique in the genus based on its single, slightly fleshy, suborbicular, convex leaf with ciliate margin, and the short subspiciform inflorescence with almost sessile flowers. A complete description is presented for this species, and data on morphology, ecology, and distribution are reported. In addition, Ornithogalum richtersveldensis, recently described from northwestern South Africa, is transferred to Eliokarmos based on its morphology and biogeography, and a new combination is presented for this species in the latter genus.This work was partly supported by H2020 Research and Innovation Staff Exchange Programme of the European Commission, project 645636: ‘Insect-plant relationships: insights into biodiversity and new applications’ (FlyHigh), and the grants ACIE18–03 UAUSTI18–02 and UAUSTI19-08 from the University of Alicante