Conspectus CO 2 , HCO 3 – , and CO 3 2– are present in all aqueous media at pH > 4 if no major effort is made to remove them. Usually the presence of CO 2 /HCO 3 – /CO 3 2– is either forgotten or considered only as a buffer or proton transfer catalyst. Results obtained in the last decades point out that carbonates are key participants in a variety of oxidation processes. This was first attributed to the formation of carbonate anion radicals via the reaction OH • + CO 3 2– → CO 3 •– + OH – . However, recent studies point out that the involvement of carbonates in oxidation processes is more fundamental. Thus, the presence of HCO 3 – /CO 3 2– changes the mechanisms of Fenton and Fenton-like reactions to yield CO 3 •– directly even at very low HCO 3 – /CO 3 2– concentrations. CO 3 •– is a considerably weaker oxidizing agent than the hydroxyl radical and therefore a considerably more selective oxidizing agent. This requires reconsideration of the sources of oxidative stress in biological systems and might explain the selective damage induced during oxidative stress. The lower oxidation potential of CO 3 •– probably also explains why not all pollutants are eliminated in many advanced oxidation technologies and requires rethinking of the optimal choice of the technologies applied. The role of percarbonate in Fenton-like processes and in advanced oxidation processes is discussed and has to be re-evaluated. Carbonate as a ligand stabilizes transition metal complexes in uncommon high oxidation states. These high-valent complexes are intermediates in electrochemical water oxidation processes that are of importance in the development of new water splitting technologies. HCO 3 – and CO 3 2– are also very good hole scavengers in photochemical processes of semiconductors and may thus become key participants in the development of new processes for solar energy conversion. In this Account, an attempt to correlate these observations with the properties of carbonates is made. Clearly, further studies are essential to fully uncover the potential of HCO 3 – /CO 3 2– in desired oxidation processes.

A number of molecular receptors containing ruthenium(II) bipyridine moiety as fluorophore and calix[4]arene-azacrown hybrid molecule as ionophore have been synthesized and characterized. These receptors (1-4) exhibit strong 3MLCT luminescence bands in the range 613-618 nm. The cation-binding property of these fluoroionophores have been investigated with the ions Na+, K+, Mg2+, Ca2+, Cs+, Zn2+, Cd2+, Hg2+ and Pb2+ and the recognition event monitored by luminescence, 1H NMR spectroscopy, the oxidation potential of metal ion and UV/Vis absorption studies. The luminescence study suggests complexation of all four receptors with Zn2+, Cd2+ and Hg2+ and for 2 and 3 also with Pb2+. The binding constants (Ks, except 4) and stoichiometries of the complexes have been calculated from the luminescence titration data, with values of Ks ranging from 2.53 x 10(5) to 6.27 x 10(3) M(-1). The 1H NMR spectroscopy study exhibits interactions of Na+ and K+ with 1 and 4, K+ and Cs+ with 2, and K+ with 3. Binding constants with these metal ions have been calculated from 1H NMR titrations using computer programs or by a direct method depending on the type of change in the chemical shifts observed upon addition of metal ions. Stoichiometry of the complexes has been determined from Job's plot. Electrochemical properties of 1-4 have been studied in the absence and also in the presence of selected metal ions and the shift of the oxidation potentials of the Ru(II) in the presence of guest ions suggests an interaction of Na+, Hg2+ and Pb2+ with 1 and 2 but not with 3 and 4, indicating a selective electrochemical response towards certain metal ions. The results obtained are presented and discussed in light of ion-binding properties and methods of detection.

The creatine/creatine kinase (CK) system plays a key role in cellular energy buffering and transport. In vertebrates, CK has four isoforms expressed in a tissue-specific manner. In the process of creatine biosynthesis several other important metabolites are formed. The anticancer effect of creatine had been reported in the past, and recent literature has reported low creatine content in several types of malignant cells. Furthermore, creatine can protect cardiac mitochondria from the deleterious effects of some anticancer compounds. Previous work from our laboratory showed progressive decrease of phosphocreatine, creatine and CK upon transformation of skeletal muscle into sarcoma. It was convincingly demonstrated that prominent expression of creatine-synthesizing enzymes L-arginine: glycine amidinotransferase and N-guanidinoacetate methyltransferase occurs in sarcoma, Ehrlich ascites carcinoma and sarcoma 180 cells; whereas, both these enzymes are virtually undetectable in skeletal muscle. Creatine transporter also remained unaltered in malignant cells. The anticancer effect of methylglyoxal had been known for a long time. The present work shows that this anticancer effect of methylglyoxal is significantly augmented in presence of creatine. On creatine supplementation the effect of methylglyoxal plus ascorbic acid was further augmented and there was no visible sign of tumor. Moreover, creatine and CK, which were very low in sarcoma tissue, were significantly elevated with the concomitant regression of tumor.

In neutral medium (pH 7.0) [RuIIIRuII(µ-CO3)4(OH)]4− undergoes one electron oxidation to form [RuIIIRuIII(µ-CO3)4(OH)2]4− at an E1/2 of 0.85 V vs. NHE followed by electro-catalytic water oxidation at a potential ≥ 1.5 V. When the same electrochemical measurements are performed in bicarbonate medium (pH 8.3), the complex first undergoes one electron oxidation at an Epa of 0.86 V to form [RuIIIRuIII(µ-CO3)4(OH)2]4−. This complex further undergoes two step one electron oxidations to form RuIVRuIII and RuIVRuIV species at potentials (Epa) 1.18 and 1.35 V, respectively. The RuIVRuIII and RuIVRuIV species in bicarbonate solutions are [RuIVRuIII(µ-CO3)4(OH)(CO3)]4− and [RuIVRuIV(µ-CO3)4(O)(CO3)]4− based on density functional theory (DFT) calculations. The formation of HCO4− in the course of the oxidation has been demonstrated by DFT. The catalyst acts as homogeneous water oxidation catalyst, and after long term chronoamperometry, the absorption spectra does not change significantly. Each step has been found to follow a proton coupled electron transfer process (PCET) as obtained from the pH dependent studies. The catalytic current is found to follow linear relation with the concentration of the catalyst and bicarbonate. Thus, bicarbonate is involved in the catalytic process that is also evident from the generation of higher oxidation peaks in cyclic voltammetry. The detailed mechanism has been derived by DFT. A catalyst with no organic ligands has the advantage of long-time stability.

In biological systems, ATP is the universal energy currency. Excitable cells and tissues, such as skeletal and cardiac muscle, brain, photoreceptor cells, spermatozoa and electrocytes all depend on the immediate availability of vast amounts of energy that may be used in a pulsed or fluctuating manner [1,2]. Because the adenylate pool and the ATP : ADP ratio are key regulators influencing many fundamental metabolic In vertebrates, phosphocreatine and ATP are continuously interconverted by the reversible reaction of creatine kinase in accordance with cellular energy needs. Sarcoma tissue and its normal counterpart, creatine-rich skeletal muscle, are good source materials to study the status of creatine and creatine kinase with the progression of malignancy. We experimentally induced sarcoma in mouse leg muscle by injecting either 3-methylcholanthrene or live sarcoma 180 cells into one hind leg. Creatine, phosphocreatine and creatine kinase isoform levels decreased as malignancy progressed and reached very low levels in the final stage of sarcoma development; all these parameters remained unaltered in the unaffected contralateral leg muscle of the same animal. Creatine and creatine kinase levels were also reduced significantly in frank malignant portions of human sarcoma and gastric and colonic adenocarcinoma compared with the distal nonmalignant portions of the same samples. In mice, immunoblotting with antibodies against cytosolic muscle-type creatine kinase and sarcomeric mitochondrial creatine kinase showed that both of these isoforms decreased as malignancy progressed. Expressions of mRNA of muscle-type creatine kinase and sarcomeric mitochondrial creatine kinase were also severely downregulated. In human sarcoma these two isoforms were undetectable also. In human gastric and colonic adenocarcinoma, brain-type creatine kinase was found to be downregulated, whereas ubiquitous mitochondrial creatine kinase was upregulated. These significantly decreased levels of creatine and creatine kinase isoforms in sarcoma suggest that: (a) the genuine muscle phenotype is lost during sarcoma progression, and (b) these parameters may be used as diagnostic marker and prognostic indicator of malignancy in this tissue. Abbreviations

Co II salts in the presence of HCO 3 À /CO 3 2À in aqueous solutionsa ct as electrocatalysts for water oxidation. It comprises of several key steps:( i) Ar elatively small wave at E pa % 0.71 V( vs. Ag/AgCl) owing to the Co III/II redox couple. (ii)Asecond wave is observed at E pa % 1.10 Vwith aconsiderably larger current.I nw hich the Co III undergoes oxidation to form aC o IV species. The large current is attributed to catalytic oxidation of HCO 3 À /CO 3 2À to HCO 4 À .( iii)A process with very large currents at > 1.2 Vo wing to the formation of Co V (CO 3 ) 3 À ,w hich oxidizes both water and HCO 3 À /CO 3 2À . Thesep rocesses depend on [Co II ], [NaHCO 3 ], andp H. Chronoamperometry at 1.3 Vg ives ag reen deposit. It acts as a heterogeneous catalystf or water oxidation. DFT calculations point out that Co n (CO 3 ) 3 nÀ6, n = 4, 5a re attainable at potentials similar to those experimentally observed.Scheme1.Outline of the water oxidation mechanisms. Misthe metal, n represents the highest oxidation state. [50] This figure has beenr eproduced (modified) from reference [50] with permission from the Royal Societyof Chemistry.

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Triazine dendrimers terminated with either four or eight dichlorotriazines can be prepared in high yields by reacting an amine-terminated dendrimer with cyanuric chloride. These materials exist as white powders and are stable to storage at room temperature. Sequential nucleophilic aromatic substitution with two different amine nucleophiles yields compounds that display the desired compositional diversity. Reactions conditions for the substitution were developed using a model dichlorotriazine with amine nucleophiles at -20 °C, 0 °C and 25 °C. Selective substitution is favored at lower temperatures and with more nucleophilic amine groups.