Predictive significance of bone sialoprotein and osteopontin for bone metastases in respectable non-small cell lung cancer: A retrospective study

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Background: Bone sialoprotein (BSP) and osteopontin (OPN) have been demonstrated predictive of bone metastases in breast and prostate carcinoma, consistent with the proposed role of BSP as a stimulator of bone mineralization and OPN in differentiation and activation of osteoclasts. Bone metastasis (BM) is often developed in non-small-cell lung cancer (NSCLC), but no predictive biomarker was identified for high risk of metastatic bone dissemination. Methods: 180 completely resected NSCLC patients were included in this study. 38 patients subsequently developed BM. Paraffin embedded primary tumor tissue of patients were supplied to produce a tissue microarray, and immunohistochemistry method was used for evaluation the expression of BSP and OPN. Different expressions of these two biomarkers among BM group and non-BM group were estimated by χ2 test. Bone metastasis-free survival was analyzed by Kaplan-Meier method. The prognostic impact of clinicopathologic parameters and biomarker expression was evaluated by Cox propotional hazards model. Results: BSP expression was associated with BM (P=0.027), while OPN expression could not reach statistical significance (P=0.495). Univariate analysis demonstrated that expression of BSP (P=0.036), N stage (P=0.000) and clinical stage (P=0.001) were associated with time interval to BM. Multivariate analyses showed BSP expression (RR=1.779, P=0.012) and clinical stage (RR=1.620, P=0.005) were independent prognostic factors for BM. Conclusions: BSP protein expression in the primary resected NSCLC is strongly associated with BM and could be used to identify high-risk patients. Correlation of OPN protein expression and bone metastasis need further investigation.

No significant financial relationships to disclose.

A novel role of phospho-beta-catenin in microtubule regrowth at centrosome

Beta-catenin is a biologically important molecule playing critical roles in both cell adhesion and transcriptional regulation in the Wnt pathway. Here, we show that phospho-beta-catenin (phosphorylated at Ser33/37/Thr41), which is reported to be degraded immediately after its phosphorylation, accumulated in the centrosome. Whereas phospho-mimicking mutant, S33/37/T41E-beta-catenin, could localize to the centrosome, S33A-beta-catenin that lacks the phosphorylation site lost its localization to the centrosome. Phospho-beta-catenin localized mainly to mother centrosome during the interphase and was recruited to daughter centrosome in M-phase. Depletion of beta-catenin with small interfering RNA or inhibition of its phosphorylation by LiCl treatment caused disruption of radial microtubule (MT) array and retardation of the MT regrowth during the recovery from nocodazole treatment. In addition, these treatments increased the frequency of mono-astral MT reorganization. Furthermore, overexpression of the nonphosphorylatable beta-catenin, but not the phospho-mimicking beta-catenin, markedly disrupted radial MT array and repressed the MT regrowth. In contrast, phospho-mimicking beta-catenin localized to both of the duplicated centrosomes with aberrant larger and denser radial MTs array formation. In addition, some of the cells overexpressing phospho-mimicking beta-catenin had multiple centrosomes. Taken together, this study demonstrates a novel role of phospho-beta-catenin in MT organization at the centrosomes.

A partial GDNF depletion leads to earlier age-related deterioration of motor function and tyrosine hydroxylase expression in the substantia nigra

Glial cell line-derived neurotrophic factor (GDNF) is a trophic factor for peripheral organs, spinal cord, and midbrain dopamine (DA) neurons. Levels of GDNF deteriorate in the substantia nigra in Parkinson's disease (PD). A heterozygous mouse model was created to assess whether chronic reductions in this neurotrophic factor impact motor function and the nigrostriatal dopamine system during the aging process. Due to the important role GDNF plays in kidney development, kidney function and histology were assessed and were found to be normal in both wild-type (WT) and GDNF+/- mice up to 22 months of age. Further, the animals of both genotypes had similar weights throughout the experiment. Locomotor activity was assessed for male WT and GDNF+/- mice at 4-month intervals from 4 to 20 months of age. Both GDNF+/- and WT mice exhibited an age-related decline in horizontal activity, although this was found 4 months earlier in GDNF+/- mice, at 12 months of age. Comparison of young (8 month old) and aged (20 month old) GDNF+/- and WT mice on an accelerating rotarod apparatus established a deficiency for aged but not young GDNF+/- mice, while aged WT mice performed as well as young WT mice on this task. Finally, both WT and GDNF+/- mice exhibited an age-related decrease in substantia nigra TH immunostaining, which was accelerated in the GDNF+/- mice. These behavioral and histological alterations suggest that GDNF may be an important factor for maintenance of motor coordination and spontaneous activity as well as DA neuronal function during aging, and further suggest that GDNF+/- mice may serve as a model for neuroprotective or rescue studies.

Glycolysis inhibition for anticancer treatment

Most cancer cells exhibit increased glycolysis and use this metabolic pathway for generation of ATP as a main source of their energy supply. This phenomenon is known as the Warburg effect and is considered as one of the most fundamental metabolic alterations during malignant transformation. In recent years, there are significant progresses in our understanding of the underlying mechanisms and the potential therapeutic implications. Biochemical and molecular studies suggest several possible mechanisms by which this metabolic alteration may evolve during cancer development. These mechanisms include mitochondrial defects and malfunction, adaptation to hypoxic tumor microenvironment, oncogenic signaling, and abnormal expression of metabolic enzymes. Importantly, the increased dependence of cancer cells on glycolytic pathway for ATP generation provides a biochemical basis for the design of therapeutic strategies to preferentially kill cancer cells by pharmacological inhibition of glycolysis. Several small molecules have emerged that exhibit promising anticancer activity in vitro and in vivo, as single agent or in combination with other therapeutic modalities. The glycolytic inhibitors are particularly effective against cancer cells with mitochondrial defects or under hypoxic conditions, which are frequently associated with cellular resistance to conventional anticancer drugs and radiation therapy. Because increased aerobic glycolysis is commonly seen in a wide spectrum of human cancers and hypoxia is present in most tumor microenvironment, development of novel glycolytic inhibitors as a new class of anticancer agents is likely to have broad therapeutic applications.

Targeting Hsp90 by 17-AAG in leukemia cells: mechanisms for synergistic and antagonistic drug combinations with arsenic trioxide and Ara-C

17-Allylamino-17-demethoxygeldanamycin (17-AAG) is a new anticancer agent currently in clinical trials. The ability of 17-AAG to abrogate the function of heat-shock protein Hsp90 and modulate cellular sensitivity to anticancer agents has prompted recent research to use this compound in drug combination therapy. Here we report that 17-AAG has striking opposite effects on the activity of arsenic trioxide (ATO) and ara-C. Combination of 17-AAG with ATO exhibited a synergistic effect in leukemia cells, whereas coincubation of 17-AAG and ara-C showed antagonistic activity. Mechanistic studies revealed that ATO exerted cytotoxic action by reactive oxygen species generation, and activated Akt survival pathway. 17-AAG abrogated Akt activation and enhanced the activity of ATO. In contrast, treatment of leukemia cells with 17-AAG caused a G1 arrest, a decrease in DNA synthesis and reduced ara-C incorporation into DNA, leading to antagonism. The ability of 17-AAG to enhance the antileukemia activity of ATO was further demonstrated in primary leukemia cells isolated from patients with acute myeloid leukemia and chronic lymphocytic leukemia, including cells from refractory patients. Our data suggest that combination of 17-AAG and ATO may be an effective therapeutic regimen. Caution should be exercised in using 17-AAG together with ara-C, as their combination effects are schedule dependent.

Distribution and ultrastructural localization of GEC1 in the rat CNS

We have previously demonstrated that GEC1 interacts with the kappa opioid receptor and GEC1 expression enhances cell surface expression of the receptor in Chinese hamster ovary cells. In this study, we generated an antiserum (PA629) directed against GEC1 in rabbits, characterized its specificity, and investigated distribution of GEC1 in tissues and in brain regions and spinal cord and its subcellular localization in hypothalamic neurons in the rat. Immunofluorescence staining demonstrated that PA629 recognized HA-GEC1 transfected into Chinese hamster ovary cells, but not HA-GABARAP or HA-GATE-16, although the three share high homology. Pre-incubation of PA629 with GST-GEC1, but not GST, abolished the staining. In immunoblotting, affinity-purified PA629 (PA629p) recognized GEC1, GABARAP and GATE-16. GEC1 migrated slower than GABARAP and GATE-16, with a M(r) of 16 kDa for GEC1 and M(r) of 14 kDa for GABARAP and GATE-16. Immunoblotting results showed that GEC1 level was higher in liver and brain than in lung and heart, and very low in kidney and skeletal muscle. GEC1 was present in all rat brain regions examined and spinal cord. Immunohistochemistry demonstrated that GEC1 immunoreactivity was distributed ubiquitously in the rat CNS with highly intense immunoreactivity in various brain nuclei and motor neurons of the spinal cord. Ultrastructural examination of neurons in the paraventricular nucleus of the hypothalamus showed that GEC1 was associated with endoplasmic reticulum and Golgi apparatus and distributed along plasma membranes and in cytosol. Coupled with our previous observation that GEC1 interacts with N-ethylmaleimide-sensitive factor, these findings strongly suggest that GEC1 functions in intracellular trafficking in the biosynthesis pathway and perhaps also the endocytic pathway. The widespread distribution of GEC1 suggests that GEC1 may be associated with many proteins, in addition to the kappa opioid receptor.

Optimizing the ongoing search for new treatments for Parkinson disease: Using futility designs

Many agents are being considered for treatment of Parkinson disease (PD). Given the large number of agents and the limited resources to evaluate new agents, it is essential to reduce the likelihood of advancing ineffective agents into large, long-term Phase III trials. Futility design methodology addresses this goal. The authors describe how a single-arm Phase II futility study uses a short-term outcome to compare a treatment group response to a predetermined hypothesized or historically based control response. The authors present advantages and limitations of futility designs along with examples derived from the data archive of a large Phase III efficacy study of treatments to delay PD progression, the Deprenyl And Tocopherol Antioxidative Therapy Of Parkinsonism (DATATOP) trial. Using the same control progression rate and treatment effect assumptions used to power the original DATATOP trial, the authors calculated the number of subjects needed to conduct two 12-month futility studies. DATATOP was designed to enroll 800 patients. Using data on 124 consecutive subjects randomized into each of the DATATOP treatment groups, the authors identified tocopherol as futile and deprenyl as worthy of further study. Using Phase II information, DATATOP could have been simplified from a 2 x 2 factorial design to a comparison of deprenyl vs placebo. While not testing efficacy, futility designs provide a strategy for discarding treatments unlikely to be effective in Phase III. A limitation is the dependence on historical data or hypothesized outcomes for untreated controls. Futility studies may decrease the time to identify treatments unworthy of further pursuit and reduce subjects' exposure to futile treatments.

Synergistic effect of targeting mTOR by rapamycin and depleting ATP by inhibition of glycolysis in lymphoma and leukemia cells

The mammalian target of rapamycin (mTOR) pathway plays important roles in regulating nutrient metabolism and promoting the growth and survival of cancer cells, which exhibit increased glycolysis for ATP generation. In this study, we tested the hypothesis that inhibition of the mTOR pathway and glycolysis would synergistically impact the energy metabolism in cancer cells and may serve as an effective therapeutic strategy to kill malignant cells. Using human lymphoma cells and leukemia cells, we demonstrated that the combination of rapamycin, an mTOR inhibitor, with a glycolytic inhibitor produced synergistic cytotoxic effect, as evidenced by apoptosis and cell growth inhibition assays. Mechanistic studies showed that inhibition of the mTOR pathway by rapamycin alone sufficiently suppressed the phosphorylation of the downstream molecules p70S6K and 4E-BP-1, but only caused a moderate cytostatic effect. Combination of mTOR inhibition and blockage of glycolysis synergistically suppressed glucose uptake and severely depleted cellular ATP pools, leading to significant enhancement of cell killing. In contrast, combination of rapamycin and ara-C did not increase cytotoxicity in vitro. Our findings suggest that targeting mTOR pathway in combination with inhibition of glycolysis may be an effective therapeutic strategy for hematological malignancies. This mechanism-based drug combination warrants further investigation in preclinical and clinical settings.

The diverse roles of J-proteins, the obligate Hsp70 co-chaperone

Hsp70s and J-proteins, which constitute one of the most ubiquitous types of molecular chaperone machineries, function in a wide variety of cellular processes. J-proteins play a central role by stimulating an Hsp70's ATPase activity, thereby stabilizing its interaction with client proteins. However, while all J-proteins serve this core purpose, individual proteins are both structurally and functionally diverse. Some, but not all, J-proteins interact with client polypeptides themselves, facilitating their binding to an Hsp70. Some J-proteins have many client proteins, others only one. Certain J-proteins, while not others, are tethered to particular locations within a cellular compartment, thus "recruiting" Hsp70s to the vicinity of their clients. Here we review recent work on the diverse family of J-proteins, outlining emerging themes concerning their function.

The diverse roles of J-proteins, the obligate Hsp70 co-chaperone

Hsp70s and J-proteins, which constitute one of the most ubiquitous types of molecular chaperone machineries, function in a wide variety of cellular processes. J-proteins play a central role by stimulating an Hsp70's ATPase activity, thereby stabilizing its interaction with client proteins. However, while all J-proteins serve this core purpose, individual proteins are both structurally and functionally diverse. Some, but not all, J-proteins interact with client polypeptides themselves, facilitating their binding to an Hsp70. Some J-proteins have many client proteins, others only one. Certain J-proteins, while not others, are tethered to particular locations within a cellular compartment, thus "recruiting" Hsp70s to the vicinity of their clients. Here we review recent work on the diverse family of J-proteins, outlining emerging themes concerning their function.

Telephone assistance for smoking cessation: one year cost effectiveness estimations

A randomised trial evaluated the American Cancer Society's telephone counselling service to assist smoking cessation. Counselling nearly doubles a smokers' odds of quitting and maintaining cessation for one year. The estimated cost for each case of maintained smoking cessation attributable to counselling availability is approximately 1300 dollars.

Texas Tobacco Prevention Pilot Initiative: processes and effects

The study was designed to examine how intensity of anti-smoking media campaigns and differing types of anti-smoking community-based programs influence young adolescents' tobacco use and related psychosocial variables. Sixth grade students attending 11 middle schools in eight study communities assigned to varying intervention conditions were assessed by a pre-intervention survey conducted in spring 2000. The assessment was followed by summer and fall 2000 media and community interventions that were evaluated by post-intervention data collection taking place with a new cohort of sixth graders in the same 11 schools in late fall 2000. In analyses conducted at the school level, the enhanced school and comprehensive community program conditions outperformed the no intervention program condition to reduce tobacco use and intentions to use tobacco. Combining the intensive or low media campaign with the comprehensive community program was most effective in suppressing positive attitudes toward smoking, while the enhanced school program alone was less effective in influencing attitudes. The most consistent changes, at least short-term, to reduce teen tobacco use, susceptibility to smoking and pro-smoking attitudes were achieved by combining the intensive media campaign with the comprehensive community program condition.

L-arginine increases plasma homocysteine in apoE-/-/iNOS-/- double knockout mice

Previous studies have shown that L-arginine (L-Arg) administration to apoE-/-/iNOS-/- double knockout mice (dKO) on a Western diet paradoxically results in an increase in atherosclerotic lesion size. We hypothesized that the potential beneficial effects of L-Arg could be offset, in part, by the byproducts of L-Arg catabolism, especially the atherogenic risk factor, homocysteine. In the kidney, L-Arg is converted to L-ornithine and guanidinoacetate (GAA) by L-arginine-glycine amidinotransferase. The efficient transmethylation of GAA by an S-adenosyl-methionine (SAM)-dependent methyltransferase in liver yields creatine and S-adenosylhomocysteine (SAH), which is readily hydrolyzed to homocysteine and adenosine. We, therefore, measured total plasma homocysteine in the dKO mice and control mice. We found that L-Arg supplementation caused a 37% increase in total plasma homocysteine (tHcy) levels in dKO mice compared to controls not treated with L-Arg (5.2+/-2.2 vs 3.8+/-1.5 microM Hcy, p<0.04). In a liver cell line, HepG2, addition of 10 and 50 microM GAA in the presence of 50 microM L-methionine (L-Met) increased tHcy production by approximately 1.47 (p<0.0001) and 2.3-fold (p<0.0001), respectively. In the presence of additional 100 microM L-Met, baseline homocysteine production was elevated by 20% (p<0.005), and 10 and 50 microM GAA augmented homocysteine production by an additional 1.88- (p<0.0001) and 3.4-fold (p<0.001), respectively, compared with 50 microM L-Met. These data suggest that increased concentrations of a methyl acceptor, such as L-Arg-derived GAA, drives SAM-dependent-methylation and consequent homocysteine formation. Furthermore, L-Met levels can also influence homocysteine production likely by regulating the synthesis of the methyl donor SAM. Epidemiological studies have suggested that homocysteine is a graded risk factor. In animal models, modestelevations of homocysteine can cause endothelial dysfunction and augment atherosclerosis. Our data suggest that L-arginine supplementation may contribute to vascular injury and atherogenesis under some circumstances by elevating homocysteine levels.

Increased mitochondrial biogenesis in primary leukemia cells: the role of endogenous nitric oxide and impact on sensitivity to fludarabine

B cell chronic lymphocytic leukemia (CLL) is the most prevalent adult leukemia in the Western hemisphere, yet many biological and molecular features of the disease remain undefined. CLL cells generate increased levels of radical species such as superoxide and nitric oxide (NO), which is associated with mitochondrial DNA mutations. Considering that NO levels can affect mitochondrial biogenesis, we hypothesized that the inherent nitrosative stress in CLL cells may lead to hyperactive mitochondrial biogenesis. Here we report that primary CLL cells contained significantly more mitochondria than normal lymphocytes and that their mitochondrial mass was significantly related to endogenous NO levels. Expression of the mitochondrial biogenesis factors nuclear respiratory factor-1 and mitochondrial transcription factor A was elevated in most CLL specimens examined and appeared to be related to cellular NO levels. Treatment of B cells with exogenous NO caused a substantial increase in mitochondrial mass. In vitro sensitivity of CLL cells to fludarabine was highly related to mitochondrial mass in that cells with greater mitochondrial mass were less sensitive to the drug. Taken together, our results suggest that NO is a key mediator of mitochondrial biogenesis in CLL and that modulation of mitochondrial biogenesis by NO may alter cellular sensitivity to fludarabine.

Identification of an N-terminal amino acid of the CLC-3 chloride channel critical in phosphorylation-dependent activation of a CaMKII-activated chloride current

CLC-3, a member of the CLC family of chloride channels, mediates function in many cell types in the body. The multifunctional calcium-calmodulin-dependent protein kinase II (CaMKII) has been shown to activate recombinant CLC-3 stably expressed in tsA cells, a human embryonic kidney cell line derivative, and natively expressed channel protein in a human colonic tumour cell line T84. We examined the CaMKII-dependent regulation of CLC-3 in a smooth muscle cell model as well as in the human colonic tumour cell line, HT29, using whole-cell voltage clamp. In CLC-3-expressing cells, we observed the activation of a Cl(-) conductance following intracellular introduction of the isolated autonomous CaMKII into the voltage-clamped cell via the patch pipette. The CaMKII-dependent Cl(-) conductance was not observed following exposure of the cells to 1 microm autocamtide inhibitory peptide (AIP), a selective inhibitor of CaMKII. Arterial smooth muscle cells express a robust CaMKII-activated Cl(-) conductance; however, CLC-3(-/-) cells did not. The N-terminus of CLC-3, which contains a CaMKII consensus sequence, was phosphorylated by CaMKII in vitro, and mutation of the serine at position 109 (S109A) abolished the CaMKII-dependent Cl(-) conductance, indicating that this residue is important in the gating of CLC-3 at the plasma membrane.

Surface analyses of micro-arc oxidized and hydrothermally treated titanium and effect on osteoblast behavior

Osteoblast adhesion on the implant material surface is essential for the success of any implant in which osteointegration is required. Surface properties of implant material have a critical role in the cell adhesion progress. Titanium and its alloys are widespread and increasingly used as implant material in dentistry and orthopedics because of their excellent biocompatibility, which is attributed to a passive layer of TiO2 on the surface. In this study, the micro-arc oxidizing (MAO) and hydrothermally synthesizing (HS) methods were used to modify the TiO2 layer on the titanium surface. The surface microstructure was observed by scanning electron microscopy. The surface energy was assessed. The mouse osteoblastic cell line (MC3T3-E1) was seeded on the treated surfaces to evaluate their effect on cell behavior. This included cell adhesion kinetics, cell proliferation, cell morphology, and cytoskeletal organization. The surface structure of MAO samples exhibited micropores with a diameter of 1-3 microm, whereas the MAO-HS-treated samples showed additional multiple crystalline microparticles on the microporous surface. The surface energy of MAO and MAO-HS was higher than that of titanium. The cell adhesion rate was higher on the MAO-HS surface than on the MAO and titanium surface, but without any significant difference between them. After 3 days of culture, cells proliferated significantly more on the MAO and titanium surface than on the MAO-HS surface. The cytoskeletal organization was analyzed by actin and vinculin staining on all the samples. We conclude that the MAO and MAO-HS methods change the surface energy of TiO2 layer on the titanium surface. This may have an influence on the initial cell attachment. Other surface characteristics may be involved in the cell proliferation, which is different from cell attachment on the sample surface. A longer-duration cell experiment should be conducted to see the effect on cell differentiation. Future in vivo evaluation may give further evidence to optimize the surface character of this kind of implant material.

Constitutive and TCDD-induced expression of Ah receptor-responsive genes in the pituitary

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related substances cause a wide variety of pathological alterations, with the most severe being progressive anorexia and body weight loss. These features suggest a possible involvement of the nervous system and endocrine organs, including the pituitary gland. TCDD-related toxicity is considered mainly to be mediated by the aryl hydrocarbon receptor (AHR) protein, which binds TCDD, and heterodimerizes with its partner protein, the aryl hydrocarbon receptor nuclear translocator (ARNT), and binds to xenobiotica responsive elements (XREs) in the promoter regions of biotransformation genes as well as genes involved in growth, differentiation and cellular homeostasis. In the present study, we have investigated the expression of AHR responsive genes in the pituitary of untreated and TCDD treated 129/SV/C57BL/6 mice in vivo and in pituitary cells in vitro. After TCDD or beta-naphthoflavone (beta NF) treatment, the relative levels of cytochrome P4501A1 (CYP1A1) mRNA and protein were dramatically increased in pituitary cells. The AHR repressor (AHRR) mRNA level was induced 7-13-fold by TCDD and beta NF. Furthermore, the expression of the adrenocorticotrophic hormone (ACTH) precursor, the proopiomelanocortin (POMC) gene, was investigated. A three-fold increase in POMC mRNA was observed in the pituitary of TCDD treated mice. POMC mRNA level was also increased in the pituitary cell line AtT-20 after TCDD treatment. The proteins encoded by POMC translational products, ACTH and beta-endorphin, were found with immunocytochemistry staining to be increased in AtT-20 cells after TCDD exposure. The presence of several XRE sequences in the promoter region and in the first intron of the human POMC gene suggest that the up-regulation of POMC expression in the pituitary may play a role in the endocrine alterations induced by TCDD. All together, the results point to the pituitary gland being a direct target for TCDD.

Photo-induced oxidation of a dinuclear Mn(2)(II,II) complex to the Mn(2)(III,IV) state by inter- and intramolecular electron transfer to Ru(III)tris-bipyridine

To model the structural and functional parts of the water oxidizing complex in Photosystem II, a dimeric manganese(II,II) complex (1) was linked to a ruthenium(II)tris-bipyridine (Ru(II)(bpy)(3)) complex via a substituted L-tyrosine, to form the trinuclear complex 2 [J. Inorg. Biochem. 78 (2000) 15]. Flash photolysis of 1 and Ru(II)(bpy)(3) in aqueous solution, in the presence of an electron acceptor, resulted in the stepwise extraction of three electrons by Ru(III)(bpy)(3) from the Mn(2)(II,II) dimer, which then attained the Mn(2)(III,IV) oxidation state. In a similar experiment with compound 2, the dinuclear Mn complex reduced the photo-oxidized Ru moiety via intramolecular electron transfer on each photochemical event. From EPR it was seen that 2 also reached the Mn(2)(III,IV) state. Our data indicate that oxidation from the Mn(2)(II,II) state proceeds stepwise via intermediate formation of Mn(2)(II,III) and Mn(2)(III,III). In the presence of water, cyclic voltammetry showed an additional anodic peak beyond Mn(2)(II,III/III,III) oxidation which was significantly lower than in neat acetonitrile. Assuming that this peak is due to oxidation to Mn(2)(III,IV), this suggests that water is essential for the formation of the Mn(2)(III,IV) oxidation state. Compound 2 is a structural mimic of the water oxidizing complex, in that it links a Mn complex via a tyrosine to a highly oxidizing photosensitizer. Complex 2 also mimics mechanistic aspects of Photosystem II, in that the electron transfer to the photosensitizer is fast and results in several electron extractions from the Mn moiety.