Lucia Alderighi

Bio: Lucia Alderighi is an academic researcher from University of Florence. The author has contributed to research in topics: Stability constants of complexes & Denticity. The author has an hindex of 11, co-authored 14 publications receiving 1743 citations.

Determination of protonation constants of some fluorinated polyamines by means of 13C NMR data processed by the new computer program HypNMR2000. Protonation sequence in polyamines

Abstract: The pK a values of 6-fluoro-4,8-diazadodecane-1,12-diamine (6-fluorospermine) (1), 6,6-difluoro-4,8-diazadodecane-1,12-diamine (6,6-difluorospermine) (2), 6-fluoro-4-azaoctane-1,8-diamine (6-fluorospermidine) (3) and 6,6-difluoro-4-azaoctane-1,8-diamine (6,6-difluorospermidine) (4) in D2O solution have been determined at 40 °C from 13C NMR chemical shifts data using the new computer program HypNMR2000. The enthalpies of protonation of compounds 1–4 and the parent amines spermine (5) and spermidine (6) have been determined from microcalorimetric titration data. The values of ΔH° were used to derive basicity constants relative to 25 °C. The NMR data have been analysed by two different methods to obtain information on the protonation sequence in the polyamines 1–5. The protonation sequence for spermine is related to its biological activity.

In Vivo Assessment of Free Magnesium Concentration in Human Brain by 31P MRS. A New Calibration Curve Based on a Mathematical Algorithm

Abstract: Free cytosolic [Mg2+] can be assessed in vivo by 31P MRS from the chemical shift of beta-ATP which in turn depends on the fraction of total ATP complexed to Mg2+ ions. The reliability of these in vivo measurements depends on the availability of an appropriate in vitro calibration to determine the limits of chemical shifts of unbound ATP and Mg-ATP complexes, using solutions that mimic the in vivo cytosolic conditions as far as possible. We used an algorithm and software to allow a quantitative definition of the Mg(2+)-binding molecules to build a semi-empirical equation that correlates the chemical shift of the beta-ATP signal to the [Mg2+] taking into account the amount of Mg2+ bound to all other constituents in solution. Our experiments resulted in a simple and reliable equation directly usable to assess in vivo the free cytosolic magnesium concentration of human brain by 31P MRS. Our method is also flexible enough to make it suitable for in vivo measurements of [Mg2+] in other organs and tissues.

Aqueous solution chemistry of beryllium

Abstract: Publisher Summary This chapter discusses aqueous solution chemistry of beryllium. Complexes of the beryllium ion are always 4-coordinate with, at most, minor deviations from regular tetrahedral geometry. The tetra-aqua ion is a very stable entity and substitution of one or more water molecules by monodentate ligands is not thermodynamically favorable except with fluoride, hydroxide, and phosphonate ligands. The aqueous solution chemistry of this ion is dominated by the ease of hydrolysis with the formation, principally, of the hydroxo-bridged species [Be3(OH)3(H2O)6] 3+ . Complex formation, then, is a process in which the ligand is usually competing with the hydrolysis reaction as the aqua-ion is present only in strongly acid conditions (pH less than ca. 3) where many ligands are protonated. The only monodentate ligands that can compete with hydrolysis are fluoride and phosphonates. Chelating ligands can form stable complexes with beryllium by virtue of the chelate effect. Greater use of beryllium will require the consideration of its role in the environment, and knowledge of speciation in naturally occurring waters will be needed.

Molecular basis of metal-ion selectivity and zeptomolar sensitivity by CueR

Abstract: The earliest of a series of copper efflux genes in Escherichia coli are controlled by CueR, a member of the MerR family of transcriptional activators. Thermodynamic calibration of CueR reveals a zeptomolar (10(-21) molar) sensitivity to free Cu+, which is far less than one atom per cell. Atomic details of this extraordinary sensitivity and selectivity for +1transition-metal ions are revealed by comparing the crystal structures of CueR and a Zn2+-sensing homolog, ZntR. An unusual buried metal-receptor site in CueR restricts the metal to a linear, two-coordinate geometry and uses helix-dipole and hydrogen-bonding interactions to enhance metal binding. This binding mode is rare among metalloproteins but well suited for an ultrasensitive genetic switch.

The Effects of Carboxylic Acids on the Aqueous Dispersion and Electrophoretic Deposition of ZrO2

Abstract: The agglomeration, electrokinetic properties and electrophoretic deposition behaviour of aqueous suspensions of ZrO2 with carboxylic acid additives were studied in comparison with conventional pH adjustment. It was found that citric acid imparted negative zeta-potential values and electrosteric stabilisation to particles in suspensions at all pH levels. The examination of additions of carboxylic acids to ZrO2 suspensions revealed that these reagents cause a sharp drop in zeta-potential at distinct addition levels, which correspond to surface saturation of the particles with negatively charged carboxylate groups. Adsorption cross sections of citric acid, EDTA and oxalic acid were evaluated from these results, showing that both citric acid and EDTA coordinate to ZrO2 surfaces by two carboxylate groups while oxalic acid is coordinated by one group. The use of carboxylic acids was shown to facilitate superior electrophoretic deposition in comparison with zeta-potential modification by conventional pH adjustment through improved suspension stability.