Comment on "Analysis on solvated molecules with a new energy partitioning scheme for intra- and intermolecular interactions".
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Comment↗
Biomedical subjects
I Mayer
Publications and source records attributed to I Mayer.
Bond order and valence indices: a personal account.
The paper accounts for the author's activity in developing bond order and valence indices since the early 80s. These indices represent an important conceptual link between the physical description of molecules as systems of electrons and nuclei and the chemical picture of molecules consisting of atoms kept together by bonds. They are also useful for a systematization and interpretation of the results obtained in the quantum chemical calculations, by permitting to extract from the wave function different pieces of information that may be assigned chemical significance. In some cases they can have some predictive power, too. Historically, the prototypes of such indices were introduced in the semiempirical quantum chemistry; the most important developments were Coulson's charge-bond order matrix in the simple Hückel theory and the Wiberg index in the CNDO framework. (Valence indices were also introduced in the semiempirical theory.) The definition of the ab initio bond order index emerged from the asymptotic term of the exchange energy component of the partitioning performed in the framework of the author's so-called "chemical Hamiltonian approach" using a "mixed" second quantization formalism for overlapping basis sets. They can also be introduced by studying the exchange part of the two-particle density (or of the second-order density matrix). Some properties of the bond order indices are discussed and the author's (until now unpublished) proof is also presented, showing the sufficient conditions under which the bond order index of a homonuclear diatomics is equal to the "chemist's bond order," i.e., the half of the difference between the number of electrons occupying bonding and antibonding orbitals. The ab initio valence indices are also introduced and discussed, and it is stressed that for correlated wave function the same "exchange only" definition of the bond order and valence indices should be used, which was introduced for the SCF case. The recent concept of the "atomic decomposition of identity" is also discussed and it is utilized for introducing bond orders and valences in the framework of the "3D analysis," when atoms are defined not by their basis orbitals but as regions of the three-dimensional (3D) physical space. Two versions of the 3D analysis are considered--the AIM (atoms in molecules)-type decomposing the space into disjunct atomic domains and the "fuzzy atoms" scheme in which there are no sharp boundaries between the atoms but they exhibit a continuous transition from one to another.
Journal Article↗
Energy partitioning schemes.
The paper gives an overview, generalization and systematization of the different energy decomposition schemes we have devised in the last few years by using both the 3-D analysis (the atoms are represented by different parts of the physical space) and the Hilbert space analysis in terms of the basis orbitals assigned to the individual atoms. The so called "atomic decomposition of identity" provides us the most general formalism for analyzing different physical quantities in terms of individual atoms or pairs of atoms. (The "atomic decomposition of identity" means that we present the identity operator as a sum of operators assigned to the individual atoms.) By proper definitions of the atomic operators, both Hilbert-space and the different 3-D decomposition schemes can be treated on an equal footing. Several different but closely related energy decomposition schemes have been proposed for the Hilbert space analysis. They differ by exact or approximate treatment of the three- and four-center integrals and by considering the kinetic energy as a part of the atomic Hamiltonian or as having genuine two-center components, too. (Also, some finite basis correction terms may be treated in different manners.) The exact schemes are obtained by using the "atomic decomposition of identity". In the approximate schemes a projective integral approximation is also introduced, thus the energy components contain only one- and two-center integrals. The diatomic energy contributions have also been decomposed into terms of different physical nature (electrostatic, exchange etc.) The 3-D analysis may be performed either in terms of disjunct atomic domains, as in the case of the AIM formalism, or by using the so called "fuzzy atoms" which do not have sharp boundaries but exhibit a continuous transition from one to another. The different schemes give different numbers, but each is capable of reflecting the most important intramolecular interactions as well as the secondary ones--e.g. intramolecular interactions of type C-H[...]O.
Algorithms↗
A general efficient implementation of the BSSE-free SCF and MP2 methods based on the chemical Hamiltonian approach.
We describe some details related to a new, general, and efficient implementation of the BSSE-free SCF and second-order Møller-Plesset perturbation theories of intermolecular interactions, based on the "Chemical Hamiltonian Approach" (CHA). The program is applicable for both open-shell and closed-shell systems and for an arbitrary number of interacting subsystems. With the new program the CHA method is faster than the usual "counterpoise correction" scheme for single point calculations, especially for clusters consisting of several molecules. The numerical results provided by these conceptually different schemes, however, have again found to be very close to each other. The CHA scheme is particularly good for providing truly BSSE-free MP2 data for intermolecular potentials.
Journal Article↗
Is the frequency of self-monitoring of blood glucose related to long-term metabolic control? Multicenter analysis including 24,500 patients from 191 centers in Germany and Austria.
Blood glucose measurements are generally accepted components of a modern diabetes self-management. The value of self-monitoring of blood glucose (SMBG) is, however, discussed controversially and only a few studies addressed the efficacy of SMBG under real-life conditions so far. In order to investigate whether the frequency of SMBG is related to long-term metabolic control, data from the DPV-Wiss-database, a standardized,prospective, computer-based documentation of diabetes care and outcome, were analyzed for patients with type 1(n = 19,491) and type 2 (n = 5,009) diabetes from 191 centers in Germany and Austria. Local HbA1c reference ranges were mathematically adjusted to the DCCT reference. For each patient, data from the most recent year of diabetes care were used. On average,patients with type 1 diabetes performed 4.4 blood glucose measurements/day. Corrected for age, gender, diabetes duration,on intensified (>or=4 daily injections or CSII) therapy (HbA1c reduction of 0.32% for one additional SMBG/day) compared to patients on conventional (1-3 daily injections) therapy(HbA1c-reduction of 0.16% for one additional SMBG/day). In 2,021 patients with insulin-treated type 2 diabetes (2.7 measurements/day), more frequent SMBG was associated with better metabolic control (HbA1c-reduction of 0.16% for one additionalSMBG/day, p < 0.0001), while in 2,988 patients on OAD or diet alone (2.0 measurements/day), more frequent blood glucose measurements were associated with higher HbA1c-levels(HbA1c-increase of 0.14% for one additional SMBG/day,p < 0.0001). These data indicate that more frequent SMBG are associated with better metabolic control in both, patients with type 1 and insulin-treated type 2 diabetes. Since no benefit ofSMBG on metabolic control was found in patients with type 2 diabetes on OAD or diet alone, SMBG should primarily be recommended for those patients with suboptimal metabolic control whereas the benefit of SHBG in non-insulin-treated patients with adequate HbA1c-levels remains uncertain.insulin therapy and center difference, the SMBG frequency was associated with better metabolic control (HbA1c-reduction of0.26% for one additional SMBG/day, p < 0.0001). HbA1c-reduction with higher frequency of SMBG was more pronounced in patients Blood glucose measurements are generally accepted components of a modern diabetes self-management. The value of self-monitoring of blood glucose (SMBG) is, however, discussed controversially and only a few studies addressed the efficacy of SMBG under real-life conditions so far. In order to investigate whether the frequency of SMBG is related to long-term metabolic control, data from the DPV-Wiss-database, a standardized,prospective, computer-based documentation of diabetes care and outcome, were analyzed for patients with type 1(n = 19,491) and type 2 (n = 5,009) diabetes from 191 centers in Germany and Austria. Local HbA1c reference ranges were mathematically adjusted to the DCCT reference. For each patient, data from the most recent year of diabetes care were used. On average,patients with type 1 diabetes performed 4.4 blood glucose measurements/day. Corrected for age, gender, diabetes duration,insulin therapy and center difference, the SMBG frequency wasassociated with better metabolic control (HbA1c-reduction of 0.26% for one additional SMBG/day, p < 0.0001). HbA1c-reduction with higher frequency of SMBG was more pronounced in patients on intensified (>or= 4 daily injections or CSII) therapy (HbA1c reduction of 0.32% for one additional SMBG/day) compared to patients on conventional (1-3 daily injections) therapy(HbA1c-reduction of 0.16% for one additional SMBG/day). In 2,021 patients with insulin-treated type 2 diabetes (2.7 measurements/day), more frequent SMBG was associated with better metabolic control (HbA1c-reduction of 0.16% for one additionalSMBG/day, p < 0.0001), while in 2,988 patients on OAD or diet alone (2.0 measurements/day), more frequent blood glucose measurements were associated with higher HbA1c-levels(HbA1c-increase of 0.14% for one additional SMBG/day, p < 0.0001). These data indicate that more frequent SMBG are associated with better metabolic control in both, patients with type 1 and insulin-treated type 2 diabetes. Since no benefit of SMBG on metabolic control was found in patients with type 2 diabetes on OAD or diet alone, SMBG should primarily be recommended for those patients with suboptimal metabolic control whereas the benefit of SHBG in non-insulin-treated patients with adequate HbA1c-levels remains uncertain.
Austria↗
Human osteoblast response to pulsed laser deposited calcium phosphate coatings.
Octacalcium phosphate (OCP) and Mn(2+)-doped carbonate hydroxyapatite (Mn-CHA) thin films were deposited on pure, highly polished and chemically etched Ti substrates with pulsed laser deposition. The coatings exhibit different composition, crystallinity and morphology that might affect their osteoconductivity. Human osteoblasts were cultured on the surfaces of OCP and Mn-CHA thin films, and the cell attachment, proliferation and differentiation were evaluated up to 21 days. The cells showed a normal morphology and a very good rate of proliferation and viability in every experimental time. Alkaline phosphatase activity was always higher than the control and Ti groups. From days 7 to 21 collagen type I production was higher in comparison with control and Ti groups. The level of transforming growth factor beta 1 (TGF-beta1) was lower at 3 and 7 days, but reached the highest values during following experimental times (14 and 21 days). Our data demonstrate that both calcium phosphate coatings favour osteoblasts proliferation, activation of their metabolism and differentiation.
Calcium Phosphates↗
The mechanism of action of Kahalalide F: variable cell permeability in human hepatoma cell lines.
Kahalalide F (KF) is a small natural peptide that showed activity in vitro and in vivo. The dose-limiting toxicity in clinical trials was transaminitis. We investigated the cytotoxicity of KF in cell lines from breast, ovary, prostate and colon cancers, but focused on hepatoma cell lines, performing mechanistic studies in HepG2 (IC50 = 0.3 microM) and PLC/PRF/5C (IC50 = 5 microM). Following KF exposure, HepG2 cells demonstrated profound ATP depletion, associated with cell swelling and cell blebbing, and increased permeability to propidium iodide (PI), annexin V (AV) and release of lactate dehydrogenase (LDH). PLC/PRF/5C cells retained their cell structure, but were permeable to PI and, following exposure to high concentrations of KF, to AV. The pattern of cell permeability is similar to maitotoxin, another small cytotoxic peptide, but the differential effects on the cell membrane induced by KF in HepG2 and PLC/PRF/5C suggest specific interactions with membranes or proteins. This could lead to better drug design aimed at exploiting the potential for cell selectivity.
Adenosine Triphosphate↗
Biocompatible Mn2+-doped carbonated hydroxyapatite thin films grown by pulsed laser deposition.
Mn(2+)-doped carbonated hydroxyapatite (Mn-CHA) thin films were obtained by pulsed laser deposition on Ti substrates. The results of the performed complementary diagnostic techniques, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy investigations indicate that the films are crystalline with a Ca/P ratio of about 1.64-1.66. The optimum conditions, when nearly stoichiometric crystalline thin films were deposited, were found to be 10 Pa oxygen pressure, 400 degrees C substrate temperature, and postdeposition heat treatment in water vapors at the same substrate temperature. The films were seeded with L929 fibroblast and hFOB1.19 osteoblast cells and subjected to in vitro tests. Both fibroblast and osteoblast cells have a good adherence on the Mn-CHA film and on the Ti or polystyrene references. Proliferation and viability tests showed that osteoblast cells growth on Mn-CHA-coated Ti was enhanced as compared to uncoated pure Ti surfaces. Caspase-1 activity was not affected significantly by the material, showing that Mn-CHA does not induce apoptosis of cultured cells. These results demonstrate that Mn-CHA films on Ti should provoke a faster osteointegration of the coated implants as compared to pure Ti. (c) 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 353-358, 2004.
Animals↗
Second-order Møller-Plesset perturbation theory without basis set superposition error. II. Open-shell systems.
The basis set superposition error-free second-order Møller-Plesset perturbation theory of intermolecular interactions, based on the "chemical Hamiltonian approach," which has been introduced in Part I, is applied here to open-shell systems by using a new, effective computer realization. The results of the numerical examples considered (CH(4) em leader HO, NO em leader HF) showed again the perfect performance of the method. Striking agreement has again been found with the results of the a posteriori counterpoise correction (CP) scheme in the case of large, well-balanced basis sets, which is also in agreement with a most recent formal theoretical analysis. The difficulties of the CP correction in open-shell systems are also discussed.
Journal Article↗
Energy partitioning for "fuzzy" atoms.
The total energy of a molecule is presented as a sum of one- and two-atomic energy components in terms of "fuzzy" atoms, i.e., such divisions of the three-dimensional physical space into atomic regions in which the regions assigned to the individual atoms have no sharp boundaries but exhibit a continuous transition from one to another. By proper definitions the energy components are on the chemical energy scale. The method is realized by using Becke's integration scheme and weight function permitting very effective numerical integrations.
Journal Article↗
Stent coating with titanium-nitride-oxide for reduction of neointimal hyperplasia.
BACKGROUND: Coronary stents prevent constrictive arterial remodeling but stimulate neointimal hyperplasia. Stainless steel induces a metallic foreign body reaction, which is absent for titanium. The hypothesis of the present study was that titanium renders the stent surface biologically inert, with reduced platelet and fibrinogen binding. METHODS AND RESULTS: Twelve pigs were instrumented with a stainless steel and 2 titanium-nitride-oxide-coated stents (TiNOX 1, ceramic; TiNOX 2, metallic). Animals were restudied after 6 weeks. Histological specimens of stented segments were analyzed by digital morphometry. Platelet adhesion and fibrinogen binding studies were performed in the perfusion chamber. Under in vitro conditions, TiNOX 1 showed reduced platelet adhesion (65+/-3%) compared with TiNOX 2 (72+/-5%; P<0.05) and stainless steel (71+/-4%; P<0.05). Platelet adhesion 48 hours after incubation with human plasma, however, was not different between TiNOX 1 (17+/-3%) and 2 (15+/-3%) but was significantly higher with stainless steel (23+/-2%; P<0.05). Fibrinogen binding was significantly reduced with TiNOX 2 (54+/-3%) compared with TiNOX 1 (82+/-4%, P<0.05) or stainless steel (100%, P<0.05). Histomorphometry revealed a significantly larger neointimal area in stainless steel (2.61+/-1.12 mm(2)) than in TiNOX 1-coated (1.47+/-0.84 mm(2), P<0.02) or TiNOX 2-coated (1.39+/-0.93 mm(2), P<0.02) stents. The reductions were 44% and 47%, respectively. CONCLUSIONS: TiNOX coating significantly reduces neointimal hyperplasia in stainless steel stents. The antiproliferative effect was similar for both TiNOX coatings, suggesting that the electrochemical properties are more important for attenuation of neointimal proliferation than the observed differences in platelet adhesion and fibrinogen binding.
Alloys↗
Melatonin and maturation pace in female three-spined stickleback, Gasterosteus aculeatus.
In many animals sexual maturation is controlled by the photoperiod. In mammals, the photoperiodic message is mediated via melatonin, but it is unclear whether this also applies to fishes. Administration of melatonin via the water on a schedule aimed at mimicking a short nonstimulatory photoperiod cycle has been found not to inhibit maturation in male three-spined sticklebacks, Gasterosteus aculeatus, kept under stimulatory long photoperiods. To study whether melatonin affects maturation pace, adult female sticklebacks kept under stimulatory photoperiodic regimes of Light:Dark (LD) 24:0 h (Exp. 1) or LD 16:8 h (Exp. 2) and 18 degrees were treated with melatonin (0, 20, or 80 microg/L water) via the water for 16 h per day. In addition, females were also kept under a nonstimulatory short photoperiod (LD 8:16). The time at which full maturation was achieved (running roe) was noted and the ovaries of nonovulated fish were studied histologically. Most fish under LD 24:0 and LD 16:8 matured (maturation rates in Exp. 1 and 2, respectively: control, 100 and 86%; low-dose melatonin, 83 and 93%; high-dose melatonin, 90 and 75%), whereas almost all females kept under LD 8:16 remained immature (maturation rates: 0% in Exp. 1 and 3% in Exp. 2). There was no difference in maturation pace, proportion of fish maturing, or relative ovarian weights between controls and melatonin-treated fish kept under LD 16:8. Furthermore, there was no difference in proportion of fish maturing or relative ovarian weights between controls and melatonin-treated fish kept under LD 24:0. However, LD 24:0 controls matured significantly earlier than fish receiving the high melatonin dose. Thus, there was an inhibitory effect of the high melatonin dose on maturation pace under LD 24:0. Nevertheless, this effect was small compared to the inhibitory effect of LD 8:16 treatment, suggesting that at least in this season, the major part of the photoperiodic effects in the stickleback is mediated via mechanisms other than circulating melatonin.
Animals↗
Male goldfish reproductive behaviour and physiology are severely affected by exogenous exposure to 17beta-estradiol.
Mature male goldfish were exposed to different concentrations of the natural hormone 17beta-estradiol (E2). Two methods of exposure were employed, via ingestion at 0, 1, 10 and 100 microg/g food and via the water at 0, 1 and 10 microg/l. The fish were exposed for 24-28 days during the spawning period. The males were then paired with an artificially induced, spawning female and their sexual behaviour was observed during a 15 min period. The physiological status of the fish was also examined with respect to GSI, presence of milt and spawning tubercles and the blood plasma concentration of E2. Despite the relatively short exposure period, exposure to physiological levels of E2 was shown to severely affect the male goldfish reproductive behaviour and physiology. In conclusion, the results from this study and the ability to interpret the effects on this well-studied species, show that the effects of E2, and possibly other estrogenic EDCs, have severe effects at several vital levels of male goldfish reproduction. The results also suggests that the hormone E2 can act as an endocrine disrupting chemical (EDC) in the environment.
Animal Feed↗
Both ovarian fluid and female urine increase sex steroid hormone levels in mature Atlantic salmon (Salmo salar) male parr.
We compared the ability of urine and ovarian fluid from female Atlantic salmon (Salmo salar) to stimulate increase in plasma concentrations of sex steroid hormones in mature conspecific male parr (priming effect of the stimuli). We also tested the hypothesis that prostaglandin F2alpha (PGF2alpha) may act as a priming pheromone in the tested stimulants. Individual males of salmon parr were exposed to female urine, ovarian fluid, urine-ovarian fluid mix, or PGF2alpha. Plasma concentrations of the sex steroids of 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) were higher in males exposed to urine, ovarian fluids, and PGF2alpha compared to control males. PGF2alpha and a mixture of urine and ovarian fluid also gave increased concentrations of 11-ketotestosterone (11-KT). Concentrations of PGF2alpha were higher in ovarian fluids than in urine. A behavior test with mature male parr in a fluviarium showed neither attraction to nor avoidance of 0.1 nM PGF2alpha, but plasma levels of 17,20beta-P were significantly higher in exposed males compared to controls.
Animals↗
Decreased expression of IGF-II and its binding protein, IGF-binding protein-2, in genital skin fibroblasts of patients with complete androgen insensitivity syndrome compared with normally virilized males.
The action of androgen by way of the AR is required for the development of male gonads and external genitalia. The interplay between androgens and the somatotropic axis, in particular the IGFs in sexual development, is currently under thorough investigation. The IGF system is thought to mediate the androgen action in androgen-responsive cells. To investigate the interaction of androgens with the IGF system, we compared the expression of IGFs and IGF-binding proteins in cultured genital skin fibroblasts from nine patients with the syndrome of complete androgen insensitivity with that in genital skin fibroblasts from 10 normally virilized males. Mutations in the AR gene and/or abnormalities of the AR protein in the immunoblot were detected in all complete androgen insensitivity genital skin fibroblast strains. They caused a complete failure of DHT binding. RIA and RT-PCR demonstrated that the genital skin fibroblast strains expressed IGF-II, IGF-binding protein-2, and IGF-binding protein-3, but no IGF-I. Most strikingly, complete androgen insensitivity genital skin fibroblast strains produced significantly lower IGF-II (P < 0.001; 42.2 +/- 9.7 vs. 106.9 +/- 11.8 ng/mg protein) and IGF-II mRNA (P < 0.01, by RT-PCR) than control genital skin fibroblast strains. The production of IGF-binding protein-2 was also decreased (P < 0.03) in complete androgen insensitivity genital skin fibroblasts, whereas that of IGF-binding protein-3 did not differ. Furthermore, high levels of IGF-binding protein-5 mRNA were detected in all genital skin fibroblast strains, whereby the 28-kDa band in the ligand blot, probably representing IGF-binding protein-5, was more abundant in complete androgen insensitivity genital skin fibroblasts. Exposure of the genital skin fibroblasts to T (5 x 10(-8) M) had only weak effects on the expression of IGFs and IGF-binding proteins. In conclusion, although the mechanism underlying these differences requires further study, it is conceivable that in addition to the endocrine actions of IGF-I, IGF-II and IGF-binding protein-2, as local growth factors, are involved in the mediation of androgen action and growth of genital tissues.
Androgen-Insensitivity Syndrome↗
Post-antibiotic and synergic effects of fluoroquinolones and ceftazidime in combination against Pseudomonas strains.
Infectious complications are still the leading cause of morbidity and mortality in seriously ill patients [1-3]. To combat the resistance of (mainly Gram-negative, non-fermentative) bacteria, e.g. Pseudomonas aeruginosa, to a wide spectrum of antibiotics, drug combination therapy has been widely adopted as standard clinical practice since the late 1990s. beta-Lactam combinations are not optimal and the potential of nephrotoxicity and ototoxicity from aminoglycosides has caused clinicians to evaluate new possibilities, such as combinations of fluoroquinolones and beta-lactams. We examine here the synergic and post-antibiotic effects (PAEs) of ciprofloxacin, ofloxacin and pefloxacin-ceftazidime combinations against 6 clinical Pseudomonas isolates. The fluoroquinolone-ceftazidime combinations were not only synergic against Comamonas (P.) testosteroni, but had double the PAEs of the two drugs alone. The ciprofloxacin-ceftazidime combination had a longer PAE against P. aeruginosa isolate 1 than ciprofloxacin alone. The combinations, however, did not have longer PAEs than those of the single drugs against the other 5 P. aeruginosa isolates.
Anti-Infective Agents↗
The Rac1/p38 mitogen-activated protein kinase pathway is required for interferon alpha-dependent transcriptional activation but not serine phosphorylation of Stat proteins.
The p38 mitogen-activated protein (MAP) kinase is activated during engagement of the type I interferon (IFN) receptor and mediates signals essential for IFNalpha-dependent transcriptional activation via interferon-stimulated response elements without affecting formation of the ISGF3 complex. In the present study, we provide evidence that the small GTPase Rac1 is activated in a type I IFN-dependent manner and that its function is required for downstream engagement of the p38 MAP kinase pathway. We also demonstrate that p38 is required for IFNalpha-dependent gene transcription via GAS elements and regulates activation of the promoter of the PML gene that mediates growth inhibitory responses. In studies to determine whether the regulatory effects of p38 are mediated by serine phosphorylation of Stat1 or Stat3, we found that the p38 kinase inhibitors SB203580 or SB202190 or overexpression of a dominant negative p38 mutant do not inhibit phosphorylation of Stat1 or Stat3 on Ser-727 in several IFNalpha-sensitive cell lines. Altogether these data demonstrate that the Rac1/p38 MAP kinase signaling cascade plays a critical role in type I IFN signaling, functioning in cooperation with the Stat-pathway, to regulate transcriptional regulation of IFNalpha-sensitive genes and generation of growth inhibitory responses.
DNA-Binding Proteins↗
Carbonated hydroxyapatites precipitated in the presence of Ti.
Hydroxyapatites (HA) were prepared by precipitation from an aqueous solution with Ti4+ (0-2500 microg/g) and with carbonate (0.8-4.0%) at pH 7.0. The uptake of Ti was found to be 75% of the original amounts. Stoichiometric ratios of Ca/P (1.67) were found for low carbonate samples. X-ray diffraction and IR spectroscopy have shown that samples have structural data characteristic for HA. Heat treatment and thermogravimetric analysis (20-900 degrees C) have shown carbonate decomposition enhanced by the presence of Ti and no transformation of the HA structure. It was also found that 0.2 mol of adsorbed and 0.6-0.8 mol of crystalline water are released from the samples during heating. Transmission electron microscopy revealed the formation of plate like crystals which increase in size with increase of carbonate content. Samples with high carbonate and high Ti content have irregular shape and are sensitive to electron beam irradiation as opposed to non-doped samples. Ti appears to have a destabilizing effect on HA. The incorporation of Ti in HA and the biological relevance of Ti in bone crystals is discussed.
Carbonates↗