The Interplay of manganese and nitrate in hydroxyapatite nanoparticles as revealed by pulsed EPR and DFT

The interplay of oppositely charged substitutions in the structure of hydroxyapatite (HAp) nanopowders is investigated on the atomic level by pulsed electron paramagnetic resonance (EPR) technique and ab initio density functional theory calculations. Benefits of EPR to determine Mn(2+) ions in nano-HAp samples are demonstrated. A simple approach based on the measurements of electron spin relaxation times allowed observing the strong influence of fast-relaxing Mn(2+) ions on the relaxation characteristics of the nitrate ions (NO3(-)/NO3(2-)) incorporated in trace amounts. Based on the results of ab initio calculations, we show the propensity of Mn(2+) and NO3(-)/NO3(2-) to associate within the HAp crystal lattice. This could have a direct impact on the functional properties of the material especially to resorption and ion exchange. Furthermore, such an effect can increase a propensity of undesired impurities to incorporate into the doped nanocrystals.

Synthesis and Biological Evaluation of Novel 3'-Difluorovinyl Taxoids

A series of 3'-difluorovinyl taxoids with C10 modifications, as well as those with C2 and C10 modifications, were strategically designed to block the metabolism by cytochrome P-450 3A4 enzyme and synthesized. These novel difluorovinyl taxoids were evaluated for their cytotoxicity against drug-sensitive human breast (MCF7), multidrug-resistant (MDR) human ovarian (NCI/ADR), human colon (HT-29) and human pancreatic (PANC-1) cancer cell lines. 3'-Difluorovinyl taxoids exhibit several to 16 times better activity against MCF7, HT-29 and PANC-1 cell lines and up to three orders of magnitude higher potency against NCI/ADR cell line as compared to paclitaxel. Structure-activity relationship study shows the critical importance of the C2 modifications on the activity against MDR cancer cell line, while the C10 modifications have a rather minor effect on the potency with some exceptions. The effect of the C2 modifications on potency against MCF7 cell line increases in the following order: H < F < Cl Collapse

Key Words

• anticancer agent
• taxoid
• fluoro-taxoid
• β-lactam synthon method
• difluorovinyl
• baccatin
• structure-activity relationship
• microtubules

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MESH Headings Collapse

Grants

• R01 CA077263 NCI NIH HHS
• R01 CA083185 NCI NIH HHS
• R01 CA103314 NCI NIH HHS

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Dynamics of actively mode-locked Quantum Cascade Lasers

The impact of upper state lifetime and spatial hole burning on pulse shape and stability in actively mode locked QCLs is investigated by numerical simulations. It is shown that an extended upper state lifetime is necessary to achieve stable isolated pulse formation per roundtrip. Spatial hole burning helps to reduce the pulse duration by supporting broadband multimode lasing, but introduces pulse instabilities which eventually lead to strongly structured pulse shapes that further degrade with increased pumping. At high pumping levels gain saturation and recovery between pulses leads to suppression of mode locking. In the absence of spatial hole burning the laser approaches single-mode lasing, while in the presence of spatial hole burning the mode locking becomes unstable and the laser dynamics does not reach a steady state anymore.

Syntheses and evaluation of novel fatty acid-second-generation taxoid conjugates as promising anticancer agents

Polyunsaturated fatty acids such as docosahexaenoic acid (DHA), linolenic acid, and linoleic acid were linked to the C-2' position of the second-generation taxoids that could overcome MDR caused by overexpressed ABC transporters. The new conjugates, tested in vivo, exhibited strong activity against drug-resistant colon cancer and drug-sensitive ovarian cancer xenografts in mice. Two of the new conjugates, DHA-SB-T-1214 and DHA-SB-T-1213, were found to achieve the total regression of drug-resistant and drug-sensitive tumors, respectively, in the animal models with substantially reduced systemic toxicity.

Asymmetry by Electrophilic Rearrangement of Symmetric 2-Pyridone Photodimers

[reaction: see text] Halogenation of achiral trans-2-pyridone photodimers results in 1,3-migration of an amide nitrogen and formation of a chiral structure with six stereogenic centers and well-differentiated functionality. The reactivity of this product toward nucleophiles, including the allylic halide, is dominated by participation by the amide nitrogen.

Manipulation of in vitro toxicant sensors in an ultrasonic standing wave

Multi-cellular spheroids are increasingly employed as in vitro sensors of toxicants and a single spheroid can be used as a test object. An ultrasonic standing wave trap (USWT) can hold small particles in a medium-flowing system. This study investigated the conditions for holding HepG2 spheroids in an USWT and its relevance to use in toxicity testing. It can take many hours to reach a detectable end point of cell damage in a standard cellular in vitro toxicant assay and the process might be accelerated through increased sample flow past the spheroid. A USWT was employed here to levitate and hold HepG2 spheroids stationary against a flow of 3 mm s(-1) when the acoustic pressure amplitude is 1.9 MPa. The ultrasonic drive frequency was 1.64 MHz. Acoustic microstreaming in the standing wave chamber generated 1 mm s(-1) flow past a levitated spheroid-scale (80 microm diameter) latex particle in the absence of sample through-flow. The conditions required to form aggregates of cells of a HepG2 cell line in a single half wavelength ultrasonic standing wave mini-chambers are also described here. It is argued that the manipulation capabilities demonstrated may have potential in increasing the efficiency of in vitro toxicant detection by spheroids. Preliminary, visual (unquantified) fluorescence microscopy observations of spheroids levitated in the standing wave in the presence of the toxicant DL-propranolol do suggest accelerated loss of viability compared with controls.

Generation of 36-femtosecond pulses from a ytterbium fiber laser

By optimizing the cavity dispersion map, 1.5-nJ pulses as short as 36 fs are obtained from a Yb-doped fiber laser. Residual higher-order dispersion currently limits the pulse duration, and it should be possible to generate pulses as short as 25-30 fs with Yb-doped fiber.

Comparative study of biological activity of insulins of lower vertebrates in the novel adenylyl cyclase test-system

The biological activity of insulins of lower vertebrates (teleosts-Oncorhynchus gorbuscha, Scorpaena porcus, chondrosteans-Acipenser guldenstaedti and cyclostomates-Lamperta fluviatilis) was studied and compared with that of standard pig insulin. The determination of biological activity was made using the novel adenylyl cyclase (AC) test-system based on the adenylyl cyclase signaling mechanism (ACSM) of insulin action discovered earlier by the authors. The biological activity of insulins was estimated as EC(50), i.e. concentration leading to half-maximal activating effect of the hormone (10(-11)-10(-7) M), in vitro, on adenylyl cyclase in two types of the target tissues: in membrane fractions of the muscles of rat and mollusc Anodonta cygnea. In rat, the efficiency of insulins was found to decrease in the following order: pig insulin>scorpaena insulin>gorbuscha insulin>sturgeon insulin>lamprey insulin. In the mollusc, the order was different: sturgeon insulin>scorpaena insulin>pig insulin>gorbuscha insulin. Lamprey insulin at the same concentrations did not apparently reach the maximal adenylyl cyclase activating effect. The suggestion was made that differences in the biological activity of insulins depend on the hormone structure and a number of indexes characteristic of the adenylyl cyclase test-system in the vertebrate and invertebrate tissues. The proposed adenylyl cyclase test-system is highly sensitive to insulin at physiological concentrations, has good reproduction and is easy to apply.

On the mechanism of relaxin action: the involvement of adenylyl cyclase signalling system

The molecular mechanism of relaxin action was studied taking into account the evolutionary relationship of the peptides belonging to the insulin superfamily and using the authors' previous data on the involvement of the adenylyl cyclase (AC) signalling system in the action of insulin and related peptides. Human relaxin 2 (10(-12)-10(-8) M) has been shown to cause a dose-dependent activating effect on AC in the human myometrium (+370%), in rat skeletal muscles (+117%) and the smooth foot muscles of the bivalve mollusc Anodonta cygnea (+73%). In these tissues mammalian insulin and insulin-like growth factor-1 (IGF-1) also had the AC activating effect. The order of efficiency of the above peptides based upon their ability to induce the maximal AC activating effect was as follows: relaxin > IGF-1 > insulin (human myometrium); IGF-1 > relaxin > insulin (rat skeletal muscle); molluscan insulin-like peptide > IGF-I > insulin > relaxin (molluscan muscle). The relaxin AC activating effect was inhibited with a selective tyrosine kinase blocker tyrphostin 47 and potentiated with Gpp[NH]p providing evidence for the participation of the receptor-tyrosine kinase and G-protein of the stimulatory type (Gs) in the regulatory action of relaxin. The conclusion is that the signalling chain: receptor tyrosine kinase ==> Gs protein ==> AC is involved in the mechanism of relaxin action.

Plants transformed with a cistron of a potato virus Y protease (NIa) are resistant to virus infection

An oligonucleotide carrying signals for translation initiation in plants was engineered upstream to a cDNA clone containing nucleotides 5812-7260 of the potato virus Y (PVY) genome. This fragment contains all but the first 100 5' terminal bases of the cistron encoding one of the PVY proteases (NIa) as well as the first 251 bases of the next cistron (NIb). Nicotiana tabacum cv. SR1 plants were transformed with this fragment. The presence of the NIa sequences in transformed plants was determined by hybridization or PCR, and its expression was ascertained by reverse transcription coupled to PCR. Plants expressing NIa were self-pollinated, and the R1 kanamycin-resistant progeny were rechecked for NIa expression. Several of these plants were found to be resistant to PVY infection, inasmuch as they did not develop symptoms for at least 50 days (the duration of the experiments), and no viral accumulation could be detected in their leaves by ELISA. All of the descendents of resistant homozygous R2 plants were also resistant. Several of the plants transformed with the last three cistrons of PVY (bases 5812-9704; NIa-NIb-coat protein) were also resistant to PVY. None of the transformed plants exhibited resistance to tobacco mosaic virus. Exposure of the plants to 35 degrees C for 48 hr prior to inoculation lowered, but did not abolish, resistance.