Schiff base oxovanadium(IV) complexes of phenanthroline bases showing DNA photocleavage activity at near-IR light and photocytotoxicity

Oxovanadium(IV) complexes VO(L)(B)](ClO4) (1-3) of N-2-pyridylmethylidine-2-hydroxyphenylamine (HL) Schiff base and phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido3,2-d: 2',3'-f] quinoxaline (dpq in 2) or dipyrido3,2-a: 2',3'-c] phenazine (dppz in 3), were prepared, characterized and their DNA binding property, photo-induced DNA cleavage activity and photocytotoxicity in HeLa cells studied. The crystal structure of 1 shows the presence of a VO2+ moiety in VO2N4 coordination geometry. The complexes show a d-d band at similar to 830 nm in DMF. The complexes display an oxidative V(V)-V(IV) response near 0.5 V versus SCE and a reductive V(IV)/V(III) response near -0.65 V in DMF -0.1 M TBAP. The complexes that are avid binders to CT DNA giving K-b values within 7.1 x 10(4) to 3.2 x 10(5) M-1, do not show any significant chemical nuclease activity in presence of 3-mercaptopropionic acid or glutathione. The dpq and dppz complexes are photocleavers of pUC19 DNA in UV-A light of 365 nm forming both O-1(2) and (OH)-O-center dot radicals and in near-IR light of 785 nm forming (OH)-O-center dot radicals. The dppz complex exhibits photocytotoxicity in visible light in HeLa cells (IC50 = 6.8 mu M). Flow-cytometric study on this complex shows a high sub-G1 phase in light compared to dark indicating PDT effect. (C) 2011 Elsevier B. V. All rights reserved.

Freezing of the octahedral tilt near ferromagnetic transition and appearance of a glassy phase at low temperature driven by the tilt instabilities in SrRuO3

The emergence of low temperature glassy phase in widely known itinerant ferromagnet SrRuO3 is remotely understood. In order to understand this aspect, we have undertaken a detailed temperature dependent (5-250 K) neutron diffraction study. We observe a freezing of the octahedral tilt near the ferromagnetic transition and an unusual deviation in the octahedral tilt near the onset of low temperature spin glass like phase. A reduction of the ordered magnetic moment and a decline in the total integrated magnetic intensity is observed around the temperature where the glassy behaviour starts to appear. The magnetotransport study also reveals the possibility for an additional magnetic ordering by demonstrating a peak in magnetoresistance at the low temperature side as well. The neutron diffraction study presented here provides useful information to understand the observed unusual low temperature magnetic phenomena in SrRuO3.

Crustal Deformation and Seismic History Associated with the 2004 Indian Ocean Earthquake: A Perspective from the Andaman–Nicobar Islands

The Indian Ocean earthquake of 26 December 2004 led to significant ground deformation in the Andaman and Nicobar region, accounting for ~800 km of the rupture. Part of this article deals with coseismic changes along these islands, observable from coastal morphology, biological indicators, and Global Positioning System (GPS) data. Our studies indicate that the islands south of 10° N latitude coseismically subsided by 1–1.5 m, both on their eastern and western margins, whereas those to the north showed a mixed response. The western margin of the Middle Andaman emerged by >1 m, and the eastern margin submerged by the same amount. In the North Andaman, both western and eastern margins emerged by >1 m. We also assess the pattern of long-term deformation (uplift/subsidence) and attempt to reconstruct earthquake/tsunami history, with the available data. Geological evidence for past submergence includes dead mangrove vegetation dating to 740 ± 100 yr B.P., near Port Blair and peat layers at 2–4 m and 10–15 m depths observed in core samples from nearby locations. Preliminary paleoseismological/tsunami evidence from the Andaman and Nicobar region and from the east coast of India, suggest at least one predecessor for the 2004 earthquake 900–1000 years ago. The history of earthquakes, although incomplete at this stage, seems to imply that the 2004-type earthquakes are infrequent and follow variable intervals

Synthesis, X-ray structures, and spectroscopic and electrochemical properties of (mu-oxo)bis(mu-carboxylato)diruthenium complexes having six imidazole bases as terminal ligands

Complexes [Ru2O(O2CR)(2)(1-MeIm)(6)](ClO4)(2) (la-c), [Ru2O(O2CR)(2)(ImH)(6)](ClO4)(2) (2a,b), and [Ru2O(O2CR)(2)(4-MeImH)(6)](ClO4)(2) (3a,b) with a (mu-oxo)bis(mu-carboxylato)diruthenium(III) core have been prepared by reacting Ru2Cl(O2CR)(4) with the corresponding imidazole base, viz. 1-methylimidazole (1-MeIm), imidazole (ImH), and 4-methylimidazole (4-MeImH) in methanol, followed by treatment with NaClO4 in water (R: Me, a; C6H4-p-OMe, b; C6H4-p-Me, c). Diruthenium(III,IV) complexes [Ru2O(O2CR)(2)(1-MeIm)(6)](ClO4)(3) (R: Me, 4a; C6H4-p-OMe, 4b; C6H4-p-Me, 4c) have been prepared by one-electron oxidation of 1 in MeCN with K2S2O8 in water. Complexes la, 2a . 3H(2)O, and 4a . 1.5H(2)O have been structurally characterized. Crystal data for the complexes are as follows: la, orthorhombic, P2(1)2(1)2(1), a = 7.659(3) Angstrom, b = 22.366(3) Angstrom, c = 23.688(2) Angstrom, V = 4058(2) Angstrom(3), Z = 4, R = 0.0475, and R-w = 0.0467 for 2669 reflections with F-o > 2 sigma(F-o); 2a . 3H(2)O, triclinic, , a = 13.735(3) Angstrom, b = 14.428(4) Angstrom, c = 20.515(8) Angstrom, alpha = 87.13(3)degrees, beta = 87.61(3)degrees, gamma = 63.92(2)degrees, V = 3646(2) Angstrom(3), Z = 4, R = 0.0485 and R-w = 0.0583 for 10 594 reflections with F-o > 6 sigma(F-o); 4a . 1.5H(2)O triclinic, , a = 11.969(3) Angstrom, b = 12.090(6) Angstrom, c = 17.421(3) Angstrom, alpha = 108.93(2)degrees, beta = 84.42(2)degrees, gamma = 105.97(2)degrees, V = 2292(1) Angstrom(3), Z = 2, R = 0.0567, and R-w = 0.0705 for 6775 reflections with F-o > 6 sigma(F-o). The complexes have a diruthenium unit held by an oxo and two carboxylate ligands, and the imidazole ligands occupy the terminal sites of the core. The Ru-Ru distance and the Ru-O-oxo-Ru angle in la and 2a . 3H(2)O are 3.266(1), 3.272(1) Angstrom and 122.4(4), 120.5(2)degrees, while in 4a . 1.5H(2)O these values are 3.327(1) Angstrom and 133.6(2)degrees. The diruthenium(III) complexes 1-3 are blue in color and they exhibit an intense visible band in the range 560-575 nm. The absorption is charge transfer in nature involving the Ru(III)-d pi and O-oxo-p pi orbitals. The diruthenium(III,IV) complexes are red in color and show an intense band near 500 nm. The diruthenium(III) core readily gets oxidized with K2S2O8 forming quantitatively the diruthenium(III,IV) complex. The visible spectral record of the conversion shows an isosbestic point at 545 nm for 1 and at 535 nm for 2 and 3. Protonation of the oxide bridge by HClO4 in methanol yields the [Ru-2(mu-OH)(mu-O2CR)(2)](3+) core. The hydroxo species shows a visible band al 550 nm. The pK(a) value for la is 2.45. The protonated species are unstable. The 1-MeIm species converts to the diruthenium(III,IV) core, while the imidazole complex converts to [Ru(ImH)(6)](3+) and some uncharacterized products. Complex [Ru(ImH)(6)](ClO4)(3) has been structurally characterized. The diruthenium(III) complexes are essentially diamagnetic and show characteristic H-1 NMR spectra indicating the presence of the dimeric structure in solution. The diruthenium(III,IV) complexes are paramagnetic and display rhombic EPR spectral features. Complexes 1-3 are redox active. Complex 1 shows the one-electron reversible Ru-2(III)/(RuRuIV)-Ru-III, one-electron quasireversible (RuRuIV)-Ru-III/Ru-2(IV), and two-electron quasireversible Ru-2(III)/Ru-2(II) couples near 0.4, 1.5, and -1.0 V vs SCE In MeCN-0.1 M TBAP, respectively, in the cyclic and differential pulse voltammetric studies. Complexes 2 and 3 exhibit only reversible Ru-2(III)/(RuRuIV)-Ru-III and the quasireversible (RuRuIV)-Ru-III/Ru-2(IV) couples near 0.4 and 1.6 V vs SCE, respectively, The observation of a quasireversible one-step two-electron transfer reduction process in 1 is significant considering its relevance to the rapid and reversible Fe-2(III)/Fe-2(II) redox process known for the tribridged diiron core in the oxy and deoxy forms of hemerythrin.

Oxovanadium(IV)-based near-IR PDT agents: design to biological evaluation

An oxovanadium(IV) complex of dipyridophenazine, as a potent metal-based PDT agent, shows efficient DNA photocleavage activity at near-IR region and high photocytotoxicity in both UV-A and visible light in HeLa cells.

Identification and thermodynamic characterization of molten globule states of periplasmic binding proteins

Molten globule-like intermediates have been shown to occur during protein folding and are thought to be involved in protein translocation and membrane insertion. However, the determinants of molten globule stability and the extent of specific packing in molten globules is currently unclear. Using far- and near-UV CD and intrinsic and ANS fluorescence, we show that four periplasmic binding proteins (LBP, LIVBP, MBP, and RBP) form molten globules at acidic pH values ranging from 3.0 to 3.4. Only two of these (LBP and LIVBP) have similar sequences, but all four proteins adopt similar three-dimensional structures. We found that each of the four molten globules binds to its corresponding ligand without conversion to the native state. Ligand binding affinity measured by isothermal titration calorimetry for the molten globule state of LIVBP was found to be comparable to that of the corresponding native state, whereas for LBP, MBP, and RBP, the molten globules bound ligand with approximately 5-30-fold lower affinity than the corresponding native states. All four molten globule states exhibited cooperative thermal unfolding assayed by DSC. Estimated values of Delta C-p of unfolding show that these molten globule states contain 28-67% of buried surface area relative to the native states. The data suggest that molten globules of these periplasmic binding proteins retain a considerable degree of long range order. The ability of these sequentially unrelated proteins to form highly ordered molten globules may be related to their large size as well as an intrinsic property of periplasmic binding protein folds.

Molecular theory of solvation and solvation dynamics of a classical ion in a dipolar liquid

A microscopic theory of equilibrium solvation and solvation dynamics of a classical, polar, solute molecule in dipolar solvent is presented. Density functional theory is used to explicitly calculate the polarization structure around a solvated ion. The calculated solvent polarization structure is different from the continuum model prediction in several respects. The value of the polarization at the surface of the ion is less than the continuum value. The solvent polarization also exhibits small oscillations in space near the ion. We show that, under certain approximations, our linear equilibrium theory reduces to the nonlocal electrostatic theory, with the dielectric function (c(k)) of the liquid now wave vector (k) dependent. It is further shown that the nonlocal electrostatic estimate of solvation energy, with a microscopic c(k), is close to the estimate of linearized equilibrium theories of polar liquids. The study of solvation dynamics is based on a generalized Smoluchowski equation with a mean-field force term to take into account the effects of intermolecular interactions. This study incorporates the local distortion of the solvent structure near the ion and also the effects of the translational modes of the solvent molecules.The latter contribution, if significant, can considerably accelerate the relaxation of solvent polarization and can even give rise to a long time decay that agrees with the continuum model prediction. The significance of these results is discussed.

Study of magnetic field effect on the specific heat and entropy in DyBa2Cu3O7-x

The change in the specific heat by the application of magnetic field up to 161 for high temperature superconductor system for DyBa2Cu3O7-x by Revaz et al. [23] is examined through the phenomenological Ginzburg-Landau(G-L) theory of anisotropic Type-II superconductors. The observed specific heat anomaly near T-c with magnetic field is explained qualitatively through the expression <Delta C > = (B-a/T-c) t/(1 - t)(alpha Theta(gamma)lambda(2)(m)(0)), which is the anisotropic formulation of the G-L theory in the London limit developed by Kogan and coworkers; relating to the change in specific heat Delta C for the variation of applied magnetic field for different orientations with c-axis. The analysis of this equation explains satisfactorily the specific heat anomaly near T-c and determines the anisotropic ratio gamma as 5.608, which is close to the experimental value 5.3 +/- 0.5given in the paper of Revaz et al. for this system. (C) 2010 Elsevier B.V. All rights reserved.

Ferrocene-Promoted Photoactivated DNA Cleavage and Anticancer Activity of Terpyridyl Copper(II) Phenanthroline Complexes

Ferrocene-appended copper(II) complexes [Cu( Fc-tpy)(B)](ClO4)(2) (1-3) and [Cu(Ph-tpy)(dppz)](ClO4)(2) (4) as control, where Fc-tpy is 4'-ferroceny1-2,2':6',2 ''-terpyridine, Ph-tpy is 4'-pheny1-2,2':6',2 ''-terpyridine, and B is a phenanthroline base, viz., 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and structurally characterized, and their DNA binding, photoactivated DNA cleavage activity, and cytotoxic properties were studied [Fe = (eta(5)-C5H4)Fe-11(eta(5)-C5H5)]. Complexes 1 and 3 as hexafluorophosphate salts were structurally characterized by X-ray crystallography. Molecular structures of [Cu(Fc-tpy)(phen)](PF6)(2) (1a) and [Cu(Fc-tpy)(dppz)](PF6)(2)center dot MeCN (3a center dot MeCN) show a distorted square-pyramidal geometry at copper(II), with the Fc-tpy ligand and the phenanthroline base showing respective tridentate and bidentate binding modes. The phenanthroline base exhibits axial-equatorial bonding, while the Fc-tpy ligand binds at the basal plane. The complexes showed quasi-reversible cyclic voltammetric responses near 0.45 and -0.3 V vs SCE in aqueous DMF-0.1 M KCl assignable to the Fc(+)-Fc and Cu(II) Cu(1) redox couples, respectively. The complexes bind to DNA, giving K-b values of 1.4 x 10(4) to 5.6 x 10(5) M-1 in the order 4 similar to 3 > 2 > 1. Thermal denaturation and viscometric titration data suggest groove and/or partial intercalative mode of DNA binding of the complexes. The complexes showed chemical nuclease activity in the presence of 3-mercaptopropionic acid (0.5 mM) or H2O2 (0.25 mM). Complexes 2-4 showed plasmid DNA cleavage activity in visible light, forming (OH)-O-center dot radicals. The Fc-tpy complex 3 showed better DNA photocleavage activity than its Ph-tpy analogue. The ferrocene moiety in the dppz complex 3 makes it more photocytotoxic than the Ph-tpy analogue 4 in HeLa cells.

Laser Surface Alloying of a Creep Resistant Magnesium Alloy MRI 230D with Al and Al2O3

A creep resistant permanent mould cast Mg alloy MRI 230D was laser surface alloyed with Al and a mixture of Al and Al2O3 using pulsed Nd:YAG laser irradiation at four different scan speeds in order to improve the corrosion and wear resistance. The microstructure, corrosion and wear behavior of the laser surface alloyed material is reported in this manuscript. The coating comprised of a featureless microstructure with cellular-dendritic microstructure near the interface and exhibited good interfacial bonding. A few solidification cracks reaching down to substrate were also observed. The two step coating with Al followed by a mixture of Al and Al2O3 exhibited a slightly better corrosion resistance than the single step coating with Al. In the long run, however, corrosion resistance of both the coatings became comparable to the as-cast alloy. The corroded surface of the laser surface alloyed specimens revealed a highly localized corrosion. The laser surface alloyed specimens exhibited an improvement in wear resistance. The laser scan speed did not exhibit a monotonic trend either in corrosion or wear resistance.

An Experimental and Numerical Study of Calliphora Wing Structure

Experiments are performed to determine the mass and stiffness variations along the wing of the blowfly Calliphora. The results are obtained for a pairs of wings of 10 male flies and fresh wings are used. The wing is divided into nine locations along the span and seven locations along the chord based on venation patterns. The length and mass of the sections is measured and the mass per unit length is calculated. The bending stiffness measurements are taken at three locations, basal (near root), medial and distal (near tip) of the fly wing. Torsional stiffness measurements are also made and the elastic axis of the wing is approximately located. The experimental data is then used for structural modeling of the wing as a stepped cantilever beam with nine spanwise sections of varying mass per unit lengths, flexural rigidity (EI) and torsional rigidity (GJ) values. Inertial values of nine sections are found to approximately vary according to an exponentially decreasing law over the nine sections from root to tip and it is used to calculate an approximate value of Young's modulus of the wing biomaterial. Shear modulus is obtained assuming the wing biomaterial to be isotropic. Natural frequencies, both in bending and torsion, are obtained by solving the homogeneous part of the respective governing differential equations using the finite element method. The results provide a complete analysis of Calliphora wing structure and also provide guidelines for the biomimetic structural design of insect-scale flapping wings.

Reactivity Of Pph3 Toward Ruiiruiiicl(O2car)4 - Syntheses, Molecular-Structures, And Spectroscopic And Electrochemical Properties Of Ruiiruiii(Oh2)Cl(Mecn)(O2car)4(Pph3)2 And Ruii2(Oh2)(Mecn)2(O2car)4(Pph3)2

By the reaction of Ru2Cl(O2CAr)4 (1) and PPh3 in MeCN-H2O the diruthenium(II,III) and diruthenium(II) compounds of the type Ru2(OH2)Cl(MeCN)(O2CAr)4(PPh3)2 (2) and Ru2(OH2)(MeCN)2(O2CAr)4(PPh3)2 (3) were prepared and characterized by analytical, spectral, and electrochemical data (Ar is an aryl group, C6H4-p-X; X = H, OMe, Me, Cl, NO2). The molecular structure of Ru2(OH2)Cl(MeCN)(O2CC6H4-p-OMe)4(PPh3)2 was determined by X-ray crystallography. Crystal data are as follows: triclinic, P1BAR, a = 13.538 (5) angstrom, b = 15.650 (4) angstrom, c = 18.287 (7) angstrom, alpha = 101.39 (3)-degrees, beta = 105.99 (4)-degrees, gamma = 97.94 (3)-degrees, V = 3574 angstrom 3, Z = 2. The molecule is asymmetric, and the two ruthenium centers are clearly distinguishable. The Ru(III)-Ru(II), Ru(III)-(mu-OH2), and Ru(II)-(mu-OH2) distances and the Ru-(mu-OH2)-Ru angle in [{Ru(III)Cl(eta-1-O2CC6H4-p-OMe)(PPh3)}(mu-OH2)(mu-O2CC6H4-p-OMe)2{Ru(II)(MeCN)(eta-1-O2CC6H4-p-OMe)(PPh3)}] are 3.604 (1), 2.127 (8), and 2.141 (10) angstrom and 115.2 (5)-degrees, respectively. The compounds are paramagnetic and exhibit axial EPR spectra in the polycrystalline form. An intervalence transfer (IT) transition is observed in the range 900-960 nm in chloroform in these class II type trapped mixed-valence species 2. Compound 2 displays metal-centered one-electron reduction and oxidation processes near -0.4 and +0.6 V (vs SCE), respectively in CH2Cl2-TBAP. Compound 2 is unstable in solution phase and disproportionates to (mu-aquo)diruthenium(II) and (mu-oxo)diruthenium(III) complexes. The mechanistic aspects of the core conversion are discussed. The molecular structure of a diruthenium(II) compound, Ru2(OH2)(MeCN)2(O2CC6H4-p-NO2)4(PPh3)2.1.5CH2Cl2, was obtained by X-ray crystallography. The compound crystallizes in the space group P2(1)/c with a = 23.472 (6) angstrom, b = 14.303 (3) angstrom, c = 23.256 (7) angstrom, beta = 101.69 (2)-degrees, V = 7645 angstrom 3, and Z = 4. The Ru(II)-Ru(II) and two Ru(II)-(mu-OH2) distances and the Ru(II)-(mu-OH2)-Ru(II) angle in [{(PPh3)-(MeCN)(eta-1-O2CC6H4-p-NO2)Ru}2(mu-OH2)(mu-O2CC6H4-p-NO2)2] are 3.712 (1), 2.173 (9), and 2.162 (9) angstrom and 117.8 (4)-degrees, respectively. In both diruthenium(II,III) and diruthenium(II) compounds, each metal center has three facial ligands of varying pi-acidity and the aquo bridges are strongly hydrogen bonded with the eta-1-carboxylato facial ligands. The diruthenium(II) compounds are diamagnetic and exhibit characteristic H-1 NMR spectra in CDCl3. These compounds display two metal-centered one-electron oxidations near +0.3 and +1.0 V (vs SCE) in CH2Cl2-TBAP. The overall reaction between 1 and PPh3 in MeCN-H2O through the intermediacy of 2 is of the disproportionation type. The significant role of facial as well as bridging ligands in stabilizing the core structures is observed from electrochemical studies.

Cobalt(II) complexes of terpyridine bases as photochemotherapeutic agents showing cellular uptake and photocytotoxicity in visible light

Cobalt(II) complexes of terpyridine bases Co(L)(2)](ClO4)(2) (1-3), where L is 4'-phenyl-2,2':6',2''-terpyridine (ph-tpy in 1), 4'-(9-anthracenyl)-2,2':6',2''-terpyridine (an-tpy in 2) and 4'-(1-pyrenyl)-2,2':6',2''-terpyridine (py-tpy in 3), are prepared and their photo-induced DNA and protein cleavage activity and photocytotoxic property in HeLa cells studied. The 1 : 2 electrolytic and three-electron paramagnetic complexes show a visible band near 550 nm in DMF-Tris-HCl buffer. The complexes 1-3 show emission spectral bands at 355, 421 and 454 nm, respectively, when excited at 287, 368 and 335 nm. The quantum yield values for 1-3 in DMF-H2O (2 : 1 v/v) are 0.025, 0.060 and 0.28, respectively. The complexes are redox active in DMF-0.1 M TBAP. The Co(III)-Co(II) and Co(II)-Co(I) couples appear as quasi-reversible cyclic voltammetric responses near 0.2 and -0.7 V vs. SCE, respectively. Complexes 2 and 3 are avid binders to calf thymus DNA giving K-b value of similar to 10(6) M-1. The complexes show chemical nuclease activity. Complexes 2 and 3 exhibit oxidative cleavage of pUC19 DNA in UV-A and visible light. The DNA photocleavage reaction of 3 at 365 nm shows formation of singlet oxygen and hydroxyl radical species, while only hydroxyl radical formation is evidenced in visible light. Complexes 2 and 3 show non-specific photo-induced bovine serum albumin protein cleavage activity at 365 nm. The an-tpy and py-tpy complexes exhibit significant photocytotoxicity in HeLa cervical cancer cells on exposure to visible light giving IC50 values of 24.2 and 7.6 mu M, respectively. Live cell imaging study shows accumulation of the complexes in the cytosol of HeLa cancer cells.

Synthesis, structure and redox properties of (?-oxo)bis(?-carboxylato)diruthenium(III) complexes containing three different terminal ligands

Blue coloured, unstable, essentially diamagnetic and non-electrolytic diruthenium(III) complexes of the formation [Ru2O(O2CR)4(en)2(PPh3)2] were prepared by reacting [Ru2O(O2CR)4(PPh3)2] with 1,2-diaminoethane (en) in CH2Cl2 (R = C6H4-p-X; X = H, Me and OMe). The molecular structure of the complexes is proposed as [{(?1-O2CR)(?1-en)(PPH3)Ru}2(?-O)(?-O2CR)2] based on the 1H NMR spectral data. The electronic spectra of the complexes display a band near 569 nm with a shoulder at 630 nm. In CH2Cl2-0.1 M [Bun4N]ClO4, the complexes exhibit redox couples Ru2III,III/Ru2III,IV and Ru2III,IV/Ru2IV,IV near 0.1 and 1.2 V (vs SCE), respectively. The potentials are the lowest among diruthenium(III) complexes with a similar core structure.

High-pressure synchrotron X-ray diffraction study of the pyrochlores: Ho2Ti2O7, Y2Ti2O7 and Tb2Ti2O7

Synchrotron-based X-ray diffraction was used to study the phase diagrams and determine the compressibilities of the pyrochlore rare-earth titanates Ho2Ti2O7, Y2Ti2O7 and Tb2Ti2O7 to 50GPa. The bulk moduli of the cubic phase of these materials were calculated to be 213 +/- 2, 204 +/- 3 and 199 +/- 1GPa, respectively. The onset of a structural phase change from cubic to monoclinic was observed near 37, 42 and 39GPa, respectively. The bulk modulus for the high pressure monoclinic phase of Y2Ti2O7 has been determined to be 185 +/- 3GPa.