Quantitative dose-response curves from subcellular lipid multilayer microarrays

The dose-dependent bioactivity of small molecules on cells is a crucial factor in drug discovery and personalized medicine. Although small-molecule microarrays are a promising platform for miniaturized screening, it has been a challenge to use them to obtain quantitative dose-response curves in vitro, especially for lipophilic compounds. Here we establish a small-molecule microarray assay capable of controlling the dosage of small lipophilic molecules delivered to cells by varying the sub-cellular volumes of surface supported lipid micro- and nanostructure arrays fabricated with nanointaglio. Features with sub-cellular lateral dimensions were found necessary to obtain normal cell adhesion with HeLa cells. The volumes of the lipophilic drug-containing nanostructures were determined using a fluorescence microscope calibrated by atomic-force microscopy. We used the surface supported lipid volume information to obtain EC-50 values for the response of HeLa cells to three FDA-approved lipophilic anticancer drugs, docetaxel, imiquimod and triethylenemelamine, which were found to be significantly different from neat lipid controls. No significant toxicity was observed on the control cells surrounding the drug/lipid patterns, indicating lack of interference or leakage from the arrays. Comparison of the microarray data to dose-response curves for the same drugs delivered liposomally from solution revealed quantitative differences in the efficacy values, which we explain in terms of cell-adhesion playing a more important role in the surface-based assay. The assay should be scalable to a density of at least 10,000 dose response curves on the area of a standard microtiter plate.

A monomeric red fluorescent protein with low cytotoxicity

Multicolour labelling with fluorescent proteins is frequently used to differentially highlight specific structures in living systems. Labelling with fusion proteins is particularly demanding and is still problematic with the currently available palette of fluorescent proteins that emit in the red range due to unsuitable subcellular localization, protein-induced toxicity and low levels of labelling efficiency. Here we report a new monomeric red fluorescent protein, called FusionRed, which demonstrates both high efficiency in fusions and low toxicity in living cells and tissues.

Are teachers of children and young adolescents responsive to suicide prevention training modules? Yes

Both before and after a 1-hour suicide prevention training module, 75 elementary teachers-in-training read a 4-sentence vignette about a suicidal student ("Pat"), then completed 8 questions about their responses. Compared with pretraining, at post-training these teachers were more likely to say that they would send or escort Pat to the counselor's office, use written or verbal no-suicide agreements, call Pat's parents, believe Pat to be serious rather than simply seeking attention, and feel comfortable handling a similar situation. Increased proactive attitudes after one hour of training imply that teachers would benefit from periodic suicide awareness and prevention training modules.

Clinicians' attitudes toward no-suicide agreements

Though no-suicide agreements are widely used and often recommended for suicidal patients, their sparse empirical support leads to questions regarding their use with patients of various ages. To answer this question, 46 licensed psychologist members of a Southern state psychology association answered questions regarding their beliefs and attitudes about no-suicide agreements. Such agreements were considered more appropriate for adults or adolescents than children. They were judged highly appropriate with moderately suicidal patients and were expected to help patients postpone suicide until after a crisis had past and to help reduce clinicians' anxiety.

Resonance Raman investigation of a soluble cytochrome c552 from alkaliphilic Bacillus firmus RAB

The environment of the heme site of a low-potential soluble cytochrome (c552) from alkaliphilic Bacillus firmus RAB has been characterized with resonance Raman scattering and compared to that of horse heart cytochrome c. The Raman data indicate that vibrational bands sensitive to the axial ligation of the heme, as well as modes sensitive to the heme peripheral environment in cytochrome c552, are distinct from those of horse heart cytochrome c. The spectra of cytochrome c552 display resonance Raman modes indicative of a methionine as the sixth ligand in the oxidized form, while the reduced form appears to contain a nitrogenous-based sixth ligand. In addition, Q-band excitation reveals differences among vibrational modes in cytochrome c552 that are sensitive to the amino acid environment surrounding the heme.

Electron microscopy of liquid crystalline DNA: direct evidence for cholesteric-like organization of DNA in dinoflagellate chromosomes

Freeze-fracture-etch replicas of concentrated DNA solutions which appeared, by polarized light microscopy, to be in a cholesteric-like liquid crystalline state were examined by high resolution transmission electron microscopy (TEM). Individual DNA molecules were resolvable, and the microscopic morphologies observed for such replicas confirmed the cholesteric organization of DNA molecules in this liquid crystalline state. Furthermore, replica morphologies were strikingly similar to TEM images of dinoflagellate chromosomes in both thin section and freeze-etch replicas, providing strong support for the cholesteric DNA packing model proposed for the organization of DNA in these chromosomes by Bouligand and Livolant.

Purification and characterization of two soluble cytochromes from the alkalophile Bacillus firmus RAB

A soluble cytochrome c and soluble cytochrome b were purified from the alkalophilic Bacillus firmus RAB. The cytochrome c, with an alpha band at 552 nm, had an apparent molecular weight of 16,500 and was acidic, with a pI of 3.4. At both pH 7.0 and 8.3, the midpoint potential of c-552 was +66 mV. Above pH 8.3, the cytochrome exhibited a pH-dependent decrease in midpoint potential. This property, among others, distinguished the cytochrome c-552 from other membrane-associated c-type cytochromes. The soluble cytochrome b, with an alpha band maximum at 558 nm, had a molecular weight of approx. 15,500 and was also an acidic protein, with a pI of 3.07. It exhibited a pH-independent midpoint potential of +28 mV.

Spectroscopic and ligand-binding properties of an oxygen-binding heme protein from Chromatium vinosum

Magnetic circular dichroism spectra were obtained for the oxidized and reduced forms of cyanide, azide and carbon monoxide complexes of an O2-binding hemeprotein isolated from the photosynthetic purple sulfur bacterium, Chronatium vinosum. Cyanide binding to the protein, which results in formation of a low-spin complex, was highly pH dependent with little complex formation observed at pH values near or below 7.

Multiple liquid crystal phases of DNA at high concentrations

DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, 'precholesteric' mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to 10 micron. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules.

Spectroscopic and kinetic properties of an oxygen-binding heme protein from Chromatium vinosum

Resonance Raman and electron paramagnetic resonance spectroscopy have been utilized to identify histidine as an axial heme ligand in a high spin, heme c-containing protein isolated from the photosynthetic purple sulfur bacterium Chromatium vinosum. Resonance Raman spectroscopy has also been used to characterize the CO adduct of the C. vinosum hemoprotein. Resonance Raman spectra of the heme site obtained within 10 ns of CO photolysis from the ferrous hemoprotein are virtually identical to those of the unligated protein, indicating that there is little or no rearrangement of the heme pocket in response to ligand photolysis. The equilibrium constant for CO binding to the ferrous hemeprotein was measured to be 1.7 X 10(-5) M-1 and the CO association rate constant determined to be 5.4 X 10(3) M-1 S-1. The quantum efficiency for photodissociation of the hemoprotein X CO complex was greater than or equal to 0.9.

Complex formation and electron transfer between mitochondrial cytochrome c and flavocytochrome c552 from Chromatium vinosum

Flavocytochrome c552 from Chromatium vinosum catalyzes the oxidation of sulfide to sulfur using a soluble c-type cytochrome as an electron acceptor. Mitochondrial cytochrome c forms a stable complex with flavocytochrome c552 and may function as an alternative electron acceptor in vitro. The recognition site for flavocytochrome c552 on equine cytochrome c has been deduced by differential chemical modification of cytochrome c in the presence and absence of flavocytochrome c552 and by kinetic analysis of the sulfide:cytochrome c oxidoreductase activity of m-trifluoromethylphenylcarbamoyl-lysine derivatives of cytochrome c. As with mitochondrial redox partners, interaction occurs around the exposed heme edge at the "front face" of cytochrome c. However, the domain recognized by flavocytochrome c552 seems to extend to the right of the heme edge, whereas the site of interaction with mitochondrial cytochrome c oxidase and reductase is more to the left. Km but not Vmax of the electron transfer reaction with mitochondrial cytochrome c increases with increasing ionic strength. The correlation of chemical modification and ionic strength dependence data indicates that the electrostatic interaction between the two hemoproteins involves fewer ionic bonds than that with other redox partners of cytochrome c.

Comparative viscometric analysis of the interaction of chloroquine and quinacrine with superhelical and sonicated DNA

Unwinding angles for the structurally related antimalarial drugs chloroquine and quinacrine have been determined with superhelical Col E1 plasmid DNA by applying the quantitative method developed by Vinograd and co-workers (Revet, B.M., Schmir, M. and Vinograd, J. (1971) Nat. New Biol. 229, 10). The value for chloroquine, 8.6 degrees, calculated assuming an unwinding angle of 26 degrees for ethidium bromide, is significantly lower than the value for quinacrine, 22.5 degrees, calculated in the same manner. Viscometric titrations with sonicated calf thymus DNA were quantitated using available binding constants for the two drugs and indicated that chloroquine also causes significantly smaller DNA length increases on intercalation relative to quinacrine. The conclusion from these experiments is that chloroquine does not bind to DNA by the classical intercalation mechanism typical of quinacrine and ethidium.

Synthesis of as-triazines as potential antiviral agents

Four acenaphtho[1,2-e]-as-triazines and 11 5,6-diaryl-as-triazines, all substituted with an aliphatic or aromatic amino function in the 3-position, were synthesized. Two acenaphthotriazines were active against vesicular stomatitis virus in tissue culture.

The interaction of propidium diiodide with self-complementary dinucleoside monophosphates

The interactions of a quinacrine derivative, methylated at both the aromatic and aliphatic nitrogens, and propidium diiodide with the dinucleoside monophosphates CpG, GpC, UpA and ApU have been investigated using 13C-NMR (for the quinacrine derivative prepared with [13C]methyl substituents and 1H-NMR and ultraviolet-visible spectroscopy. The quinacrine derivative displayed negligible interaction with the dinucleosides at concentrations up to 5 - 10(-4) M. Propidium did form complexes with dinucleosides even at concentrations as low as 10(-4) M. Propidium displayed a pyrimidine-purine binding preference and gave especially large changes in ultraviolet-visible and 1H-NMR spectra in the presence of CpG. This suggests that propidium forms an intercalated complex with a Watson-Crick hydrogen-bonded CpG dimer. At higher concentrations UpA and GpC gave similar spectral changes indicating that they could also form significant amounts of an intercalated complex with propidium under appropriate conditions. The changes caused by ApU were small under all conditions and were more similar to the effects caused by mononucleotides. These results indicate that, at least for phenanthridines, cationic side chains do not greatly inhibit complex formation with dinucleoside monophosphates, and suggest that the weak interaction of the quinacrine derivative with dinucleosides is due to weaker interactions of the acridine ring system with nucleoside bases relative to the phenanthridine ring system.

The interaction of plant alkaloids with DNA. II. Berberinium chloride

The interaction of berberinium chloride with DNA has been investigated using spectrophotometry, viscometric titrations with sonicated and closed circular superhelical DNA, and flow polarized fluorescence. The binding results for berberinium were found to fit the neighbor exclusion model. The two viscometric titrations and flow polarized fluorescence results exclusion model. The two viscometric titrations and flow polarized fluorescence results also indicated that berberinium binds to DNA by intercalation. Titration of sonicated DNA with berberinium produced viscosity increases which were less than those obtained with quinacrine and the titration of superhelical DNA indicated a significantly smaller unwinding angle for intercalation of berberinium than for quinacrine. These results can be interpreted in terms of a model in which (i) berberinium is partially intercalated into the double helix, or (ii) the alkaloid is more completely intercalated into the double helix, but causes bending of the helix due to the slight nonplanarity of the berberinium ring system, or (iii) a combination of (i) and (22).