María Savirón

Involvement of the ABCG37 transporter in secretion of scopoletin and derivatives by Arabidopsis roots in response to iron deficiency

Studies of Iron (Fe) uptake mechanisms by plant roots have focussed on Fe(III)-siderophores or Fe(II) transport systems. Iron deficency also enhances root secretion of flavins and phenolics. However, the nature of these compounds, their transport outside the roots and their role in Fe nutrition are largely unknown. We used HPLC/ESI-MS (TOF) and HPLC/ESI-MS/MS (ion trap) to characterize fluorescent phenolic-type compounds accumulated in roots or exported to the culture medium of Arabidopsis plants in response to Fe deficiency. Wild-type and mutant plants altered either in phenylpropanoid biosynthesis or in the ABCG37 (PDR9) ABC transporter were grown under standard or Fe-deficient nutrition conditions and compared. Fe deficiency upregulates the expression of genes encoding enzymes of the phenylpropanoid pathway and leads to the synthesis and secretion of phenolic compounds belonging to the coumarin family. The ABCG37 gene is also upregulated in response to Fe deficiency and coumarin export is impaired in pdr9 mutant plants. Therefore it can be concluded that: Fe deficiency induces the secretion of coumarin compounds by Arabidopsis roots; the ABCG37 ABC transporter is required for this secretion to take place; and these compounds improved plant Fe nutrition.

The synthesis of 4,4'(5')-diformyltetrathiafulvalene

The synthesis of the title compound 9, by three different routes, is described for the first time.

Synthesis and characterization of functionalized ethylenediselenotetrathiafulvalenes: A comparative study with their all-sulfur analogues

Abstract The synthesis of the first monofunctionalized and some new difunctionalized ethylenediseleno-TTF (EDS-TTF) derivatives is described, including systems with alcohol, ester and aldehyde substituents. The mass spectrometric behaviour of these compounds has been studied for the first time and a comparative electrochemical study with their all-sulfur analogues has been carried out.

Crown-annelated tetrathiafulvalenes: synthesis of new functionalised derivatives and spectroscopic and electrochemical studies of metal complexation

Synthetic routes to the first unsymmetrical annelated tetrathiafulvalene–S2O4 crowns are reported; the methodology is versatile, affording the parent system 8, functionalised derivatives 6, 7 and 9–12, and amphiphilic derivatives 6 and 13. UV–VIS spectroscopic studies of metal binding (Na+, Ag+ and Ba2+) to the crown–TTF systems 8 and 13, and the bis(crown)–TTF 14 have been performed in solution, and stability constants have been calculated. The data establish that for the crown compounds 8 and 13 1 : 1 complexes are formed, whereas for the bis(crown) compound 14 both 1 : 1 [14(Na+)] and 1 : 2 [14(Na+)2] complexes are formed. Solution electrochemical studies reveal that metal complexation to the crown unit leads to a small anodic shift in the first oxidation potential of the TTF system. Langmuir–Blodgett films of amphiphilic compound 13 have been assembled on solid substrates by Y-type deposition.

The first allylic alcohol derivatives of tetrathiafulvalene. A route to new covalently linked donors

Abstract The first allylic alcohols derived from TTF are described. They afford new multi-stage redox assemblies ( 6–8 ), including the first system containing both EDT-TTF and ferrocene moieties ( 6a ).

Conducting Langmuir–Blodgett films of an amphiphilic unsymmetrical ethylenedithiotetrathiafulvalene derivative: EDT–TTF–CH2OC(O)C17H35

Langmuir-Blodgett (LB) films of the novel amphiphilic ethylenedithiotetrathiafulvalene derivative [EDT–TTF–CH2OC(O)C17H35, 5] assembled on a range of solid substrates have room temperature in-plane do conductivity values as high σrt= 10–2–10–3 S cm–1 as deposited; iodine doping results in an immediate decrease in conductivity to values of σrt=ca. 10–6 S cm–1, which subsequently increases over a few hours to σrt=ca. 10–3 S cm–1, as a stable mixed-valence state is attained. The LB films have been characterized by ellipsometry, UV–VIS spectroscopy and cyclic voltammetry. By comparison with analogous long-chain TTF and BEDT–TTF derivatives, it appears that the carbonyl group in the side chain of 5 facilitates LB film formation, and the ethylenedithio bridge of 5 contributes to the unusually high conductivity of the as-deposited films, possibly due to the presence of non-bonded, intermolecular S—S interactions. Analogous derivatives of trimethyl-TTF and ethylenediseleno-TTF substituted with the same side-chain, i.e., triMe–TTF–CH2OC(O)C17H35, 10, and EDS–TTF–CH2OC(O)C17H35, 11, respectively, form LB films with significantly lower conductivity values than 5, both before and after iodine doping.

The synthesis of dihalotetrathiafulvalenes

The synthesis of dihalotetrathiafulvalenes has been achieved by lithiation-halogenation procedures or coupling reactions. The regioselectivity of lithiation reactions has been unambiguously determined by mass spectrometry and a previous report on the synthesis of 4,5-dichlorotetrathiafulvalene has been demonstrated to be erroneous.

4,,4'(5')-disubstituted tetrathiafulvalenes and systems with extended conjugation incorporating TTF spacers

Abstract Difunctionalised tetrathiafulvalenes 2–6 have been prepared from 4,4′(5′)-bis(methoxycarbonyl)tetrathiafulvalene ( 1 ).

New multi-redox assemblies incorporating TTF, EDT-TTF and ferrocene moieties

Abstract A range of multi-stage redox assemblies incorporating TTF, EDT-TTF and ferrocene groups have been prepared from formylTTF and formylEDT-TTF, and their electrochemical behaviour has been studied.

Metabolites involved in cellular communication among human cumulus-oocyte-complex and sperm during in vitro fertilization.

BackgroundFertilization is a key physiological process for the preservation of the species. Consequently, different mechanisms affecting the sperm and the oocyte have been developed to ensure a successful fertilization. Thus, sperm acrosome reaction is necessary for the egg coat penetration and sperm-oolema fusion. Several molecules are able to induce the sperm acrosome reaction; however, this process should be produced coordinately in time and in the space to allow the success of fertilization between gametes.The goal of this study was to analyze the metabolites secreted by cumulus-oocyte-complex (COC) to find out new components that could contribute to the induction of the human sperm acrosome reaction and other physiological processes at the time of gamete interaction and fertilization.MethodsFor the metabolomic analysis, eighteen aliquots of medium were used in each group, containing: a) only COC before insemination and after 3 h of incubation; b) COC and capacitated spermatozoa after insemination and incubated for 16–20 hours; c) only capacitated sperm after 16–20 h in culture and d) only fertilization medium as control. Six patients undergoing assisted reproduction whose male partners provided normozoospermic samples were included in the study. Seventy-two COC were inseminated.ResultsThe metabolites identified were monoacylglycerol (MAG), lysophosphatidylcholine (LPC) and phytosphingosine (PHS). Analysis by PCR and in silico of the gene expression strongly suggests that the cumulus cells contribute to the formation of the PHS and LPC.ConclusionsLPC and PHS are secreted by cumulus cells during in vitro fertilization and they could be involved in the induction of human acrosome reaction (AR). The identification of new molecules with a paracrine effect on oocytes, cumulus cells and spermatozoa will provide a better understanding of gamete interaction.