William Ware

William Ware
The University of Western Ontario | UWO · Faculty of Science

PhD

About

157
Publications
3,953
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8,460
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Additional affiliations
July 1971 - July 1996
The University of Western Ontario
Position
  • Professor (Full)

Publications

Publications (157)
Article
The importance of the P450 enzyme CYP1B1 in both cancer therapy and prevention are reviewed and evidence is discussed, which provides strong biological plausibility for the therapeutic merits of this approach. The significant resistance to chemotherapy among common cancers, and the realization that in many cases chemotherapy leaves behind drug-resi...
Article
Full-text available
The influence of heat treatment and of added coadsorbates on the surface photophysics of pyrene and naphthalene adsorbed on silica gel is reported. When the silica gel surface is partially dehydroxylated, the distribution of pyrene or naphthalene is inhomogeneous, as indicated by multiexponential fluorescence decay and broad emission spectra. Addit...
Article
Full-text available
Tryptophan fluorescence decay kinetics have been systematically investigated in aqueous solutions as a function of pH as well as in a variety of buffer solutions. Below pH 7.0, the decay appears to be double exponential with a subnanosecond component confirming the previous findings of Rayner and Szabo (3). In the low pH region, where the proton co...
Article
Full-text available
There is growing evidence that vitamin D deficiency significantly increases the risk of adverse cardiovascular events and that a vitamin D status representing sufficiency or optimum is protective. Unfortunately, in clinical trials that address interventions for reducing risk of adverse cardiovascular events, vitamin D status is not generally measur...
Article
That LDL cholesterol drives atherosclerosis is a widely if not almost universally held belief, and this belief strongly influences the mainstream approach to coronary heart disease. However heart disease has a number of stages, and in terms of primary prevention, the initiation and progression of silent or sub-clinical atherosclerosis is clearly fu...
Article
Full-text available
Recommendations for a healthy or prudent diet include a large number of daily servings of fruits and vegetables, and these 2 classes of food are widely believed to assist in cancer prevention. One potential mechanism that is rarely mentioned in nutritional studies involves the cytochrome P450 enzyme CYP1B1, which appears to have the unique properti...
Article
Fluorescent tumor markers and other chemicals that concentrate in tumors and can be utilized in photodynamic therapy to yield cytotoxins in the form of reactive oxygen species have been of interest for a number of years. In addition, the use of fluorescent markers for the purpose of tumor tissue visualization continues to be of considerable interes...
Article
There is growing evidence that the present risk assessment protocol for coronary heart disease appears to underestimate the risk in general and the presence and progression of atherosclerosis in particular. Little or no correlation has been found between the 10-year risk based on the Framingham model and the extent or progression of coronary calcif...
Article
It is well known that by far the strongest association between serum cholesterol levels and the risk of coronary heart disease or related adverse events is found in younger men. The question is - what is different about this age-gender subgroup? It has been suggested that this enhanced risk is seen in younger men because of unique exposure to stres...
Article
Abstract— An apparatus is described and an actinometric standard proposed (the intramolecular cycloaddition of the tricyclic dienedione 1) for the determination of quantum yields of reaction of substances adsorbed on silica gel.
Article
Fluorescence lifetime distributions are recovered from a dipole-dipole energy-transfer system (donor phenanthrene, acceptor acridine) in rigid and viscous media. In the case of a rigid medium, the well-known Förster equation is verified to high precision. An exact equation for the rate constant distribution predicted by Förster theory is obtained a...
Article
A method based on fluorescence lifetime distribution analysis is proposed for the determination of micellar size distributions in polydisperse systems. The exponential series method is employed to determine the lifetime distribution for a probe in the presence of quencher. This distribution is then analyzed by the maximum entropy method in order to...
Article
The ill-conditioned nature of the lifetime distribution analysis is demonstrated using the fluorescence decay data of pyrene adsorbed on variously dehydroxylated silica gel surfaces. A set of physically plausible results can be obtained only after a regularization technique is employed in the data reduction. This study indicates that a bimodal dist...
Article
In a lifetime distribution analysis of six polycyclic aromatic hydrocarbons (PAHs) adsorbed on silica gel surfaces, a dramatic photophysical effect on the surface can be seen in the PAHs where the lowest excited singlet state is of 1L(b) type. This suggests that this effect is related to the symmetry of the lowest excited singlet state of the parti...
Article
The fluorescence quantum yields of six polycyclic aromatic hydrocarbons (PAHs) adsorbed on both hydroxylated and highly dehydroxylated silica gel surfaces have been measured, using a diffuse reflectance method, an integrating sphere method, and a secondary method based on diffuse reflectance. Consistent results were obtained from these different pr...
Article
The fluorescence lifetime of the dye Kiton Red S in monodispersed polystyrene colloids was measured by using the single-photon-counting technique. The measured lifetime changed from 1.6 ns when the dye was in water to 3–4 ns when it was in colloidal suspensions of various monodispersed polystyrene microspheres. Interaction of electrons of the dye m...
Article
This work describes a stroboscopic optical boxcar technique for the determination of fluorescence lifetimes which achieves performance comparable to techniques such as time‐correlated single photon counting or phase modulation. The stroboscopic technique is based on the use of a traveling wave injected into a delay line connecting the dynodes of a...
Article
Full-text available
Addition of the polyene antibiotic amphotericin B or tissue culture medium to nondifferentiated HL-60 cells in the presence of luminol induces a chemiluminescence signal that reaches a peak value within a few seconds and decays exponentially in less than a minute. The kinetics of the signal and its modulation by superoxide dismutase, catalase, and...
Article
The fluorescence decay of pyrene in SDS micelles has been investigated with the use of the maximum entropy method (MEM). Lifetime distributions, especially broad at low SDS concentrations, have been recovered. Simultaneous studies of the Ham effect and the water-induced fluorescence band of 4-(9-anthryl)-N,N-dimethylaniline (ADMA) suggest that the...
Article
The maximum entropy method and a new more robust exponential series method are described and tested for the recovery of underlying fluorescence lifetime distributions derived from digital fluorescence data. Both real and simulated data are used in this study. Except for the resolution of single-lifetime systems, it is found that the two methods are...
Article
The fluorescence decay of the monomer emission band of 1,3-di(1-pyrenyl)propane has been investigated at different temperatures in order to test models implying either the presence of three distinct species (one monomer and two excimers) or a more complex situation, giving rise to lifetime distributions. The decay curves were analyzed by free-float...
Article
The maximum entropy method (MEM) has been used to analyze fluorescence decays of pyrene quenched by Cu2+ ions in micellar SDS solutions. Two new methods for precise determination of kinetic parameters have been introduced. The Poisson distributions of preexponential factors have been recovered explicitly from the fluorescence decay data.
Article
The Maximum Entropy Method and a new Exponential Series Method are described and tested for the recovery of underlying fluorescence lifetime distributions from digital fluorescence decay data. These two numerical techniques are applied to two heterogeneous systems, the intramolecular quenching in 1,3-di(1-pyrenyl)propane and the cupric ion quenchin...
Conference Paper
This paper discusses the problem of fluorescent molecular systems where the complexity of the molecule or its environment give rise to distributions of decay times rather than discrete two- or three-component decay behavior. The Exponential Series Method for distribution recovery is examined and examples from recent work presented.
Article
Analysis of fluorescence decay data for probes incorporated into model or biological membranes invariably requires fitting to more than one decay time even though the same probe exhibits nearly single-exponential decay in solution. The parinaric acids (cis and trans) are examples of this. Data are presented for both parinaric acid isomers in dimyri...
Article
The decay kinetics of the monomer fluorescence band of 1,3-di(1-pyrenyl) propane has been studied by the time-correlated single-photon counting technique. Analysis by the exponential series method has revealed an existence of a short-lifetime distribution in addition to two longer-lived fluorescence components. This is in contradiction with the pre...
Article
The fluorescence decay of homotryptophan derivatives was investigated at high precision as a function of temperature and viscosity. The data were analyzed by the exponential series method for the determination of fluorescence lifetime distributions. In all cases the fluorescence decay was found to be described by a distribution of lifetimes. The li...
Article
Lifetime distributions have been recovered from fluorescence decay curves of p-(9-anthryl)-N,N-dimethylaniline (ADMA) and its methylated derivative 4-(9-anthryl)-3,5-dimethyl-N,N-dimethylaniline (ADDMA) in 2-propanol with the use of the exponential series method (ESM). The lifetime distributions are attributed to the diversity of conformers and seq...
Conference Paper
Distributions of fluorescence lifetimes which underly a fluorescence decay curve may be recovered by a straightforward analytical procedure. The procedure is model independent and requires no previous knowledge of the underlying distribution. The procedure has been tested on a variety of simulated and real data and applied to real experimental syst...
Article
Fluorescence decay curves exhibiting good deconvolution fits to two or three exponentials can be interpreted in terms of two or three distinct lifetimes or as the result of complex underlying distributions which are not evident because of statistical noise. This work deals with the recovery of complex distributions of lifetimes from single photon d...
Article
The fluorescence decay of a series of indole-3-alkanoic acids has been studied as a function of pH. Each successive member of the series varies only by the addition of a methylene group to the unbranched alkane side chain. In the pH region near the acid pKa, extra fluorescence decay lifetimes appear which cannot be assigned to only the ionized and...
Article
Homotryptophan (HTRP) is the analog of tryptophan (TRP) with one additional methylene separating the indole ring from the amino acid moiety. HTRP has very similar fluorescence properties to TRP in that it exhibits two lifetimes associated with the zwitterion and one lifetime associated with the anion. This behaviour is not readily explained by the...
Article
The effect of distributions of lifetimes on the recovered fluorescence decay parameters is examined by model calculations. The most notable results are that only two lifetimes are necessary to fit adequately a single Gaussian distribution, that the Stern-Volmer plots behave “normally” and that a bimodal distribution is also adequately described by...
Article
It is shown that single-photon-counting fluorescence decay data fit to a two-component decay law yielding satisfacory fit statistics and random residuals can conceal underlying sets of lifetimes with a variety of intensity distribution functions of remarkable width and diversity of shape. Only by collecting data to a large number of counts per chan...
Article
The effect of temperature on the fluorescence quenching of pyrene adsorbed on silica gel by 2-bromonaphthalene has been studied. These studies have yielded activation energies for diffusion on a silica gel surface. Activation energies of 4 and 2 kcal mol-1 were obtained respectively for the quenching of pyrene on "dry" silica gel and for decanol-co...
Article
The emission of aromatic hydrocarbons, in particular that of pyrene, adsorbed on silica gel serves as a surface probe. The changes in silica gel structure imposed by heat treatment in vacuum (700 degree C) are revealed in poorly resolved spectra, multiple exponential fluorescence decay, ground state association and shortened lifetimes for pyrene em...
Article
Steady-state and time-resolved fluorescence studies of fluorescein (Fl) and 9-hydroxyphenylfluoron (HPF) bound to high-affinity rabbit anti-Fl IgG antibody (anti-Fl IgG) have been performed. The heterogeneity in the fluorescence properties observed for Fl bound to anti-Fl IgG is reduced for HPF bound to anti-Fl IgG. A charge transfer between a tryp...
Article
The time dependence of the fluorescence of tryptophan (Trp) and indole in ethylene glycol/water solution has been investigated in the temperature region 77-300 K. It has previously been observed that the large Stokes shift in the indole emission disappears at low temperature. Time-resolved spectra of indole as a function of temperature show that wh...
Article
Variation in the heat treatment of silica gel, and thus its degree of hydration, prior to the adsorption of pyrene and the quencher 2-bromonaphthalene (BN) onto the surface, influences the rate of quenching of pyrene fluorescence. The quenching rate is slow with dry silica gel whereas on dry silica gel treated with additives such as water or 1-deca...
Article
In agreement with the results reported by Lipsky, emission from cyclohexane depends on the temperature T and on the nature of the phase (liquid or solid). Determination of the lifetimes of the fluorescent state with a single photon counting apparatus gives similar results. Our experimental work shows that the rate constant of fluorescence for the s...
Article
The fluorescence decay and fluorescence spectra of 5-methoxytryptophan in water have been recorded as a function of pH. The fluorescence spectrum undergoes a pronounced red-shift as the pH is increased. This behaviour is ascribed to deprotonation of the alanyl amino group. This is the first direct evidence for an effect of the nature of the substit...
Article
The performance characteristics of the Hamamatsu R928 side‐window photomultiplier tube have been evaluated in the picosecond time domain. This phototube is proposed as an attractive solution to the problem of high time resolution when a sync‐pumped dye laser is combined with the single‐photon time correlation method for determining fluorescence lif...
Article
The fluorescence properties of tryptophan in water and deuterated water have been examined. Tryptophan molecules exhibit three distinct fluorescence lifetimes in water which become longer in deuterated water; the two shorter lifetimes are present below the pK of the amino group and the long lifetime appears as the pH is raised through this pK. The...
Article
The effects of coadsorbed molecules on the emission of pyrene and the dimerization of acenaphthylene have been studied on silica gel. Alkanols, acenaphthene, glycerol, malonic acid, and 1-adamantanol were the coadsorbates used. The stronger adsorbates apparently displace pyrene from the preferred adsorption sites, reduce the concentration of ground...
Article
The influence of steric interference with sandwich-type exciplex formation has been investigated by using mono-and di-tert-butyl substitution of N,N-dimethylaniline (DMA). Pyrene was the electron acceptor and studies were carried out with both steady-state and fluorescence lifetime techniques in hexane and tetrahydrofuran (THF). All the rate consta...
Chapter
Early interest in diffusion-controlled processes centered around the coagulation of colloidal particles. These particles were large enough that the solvent provided an almost perfect continuum for diffusion. Fick’s laws were invoked and concentration-independent diffusion coefficients employed. It was assumed that one could use a mutual diffusion c...
Chapter
After a brief review of the history of pulse fluorometry, various aspects of the single-photon technique will be described and discussed. The main aim is to provide a basis for the more specialized contributions to follow. Topics to be discussed will include pulsed light sources, detection systems, general theory of distortions, and time-resolved s...
Chapter
After a brief history of the exciplex and excimer, the photophysics of systems exhibiting molecular association both in the ground and excited states will be discussed. The emphasis will be on kinetic models, the measurement of rate constants associated with these models, and the determination of activation parameters and equilibrium thermodynamic...
Chapter
Factors influencing fluorescence decay will be examined in a general way. Complicating effects which cause systems to depart from simple kinetics will be discussed including diffusion control, ground-state complexing, exciplex and excimer főrmation and Forster transfer. Basic equations will be derived or discussed.
Article
A detailed study of the emission, excitation spectra and fluorescence decay of pyrene adsorbed on silica gel, porous Vycor, alumina, and calcium fluoride is reported. Monomer emission and a longer-wavelength broad-band emission (neither decaying with a single exponential) was observed on silica. The excitation spectrum of the broad-band emitter was...
Article
The occurrence of inter- and intragranular motion of aromatic hydrocarbons on dry silica gel has been demonstrated. Evidence presented includes (a) the observation of dimerization of acenaphthylene in static and agitated systems to give cis and trans isomers; (b) the quenching and sensitization of the dimerization of acenaphthylene; (c) the dimeriz...
Article
In this paper we present general equations for the treatment of sensitized reactions when two different ecxited states of the sensitizer both contribute to the photosensitization. In the case of diffusion-controlled reactions, classical equations based on stationary diffusion are not valid under the usual experiemental conditions and have to be mod...
Article
Analysis of the measurement of the quantum yield ϕ of diffusion-controlle energy transfer of an electronically excited molecule A* towards an acceptor B leads in principle to the determination of the lifetime τo and the quantum yield φo of formation of A*. However, for short lifetimes of the donor A*, the classical linear expression between 1/ϕ and...
Article
Part one of this report deals with attempts over the past several years to devise a more sophisticated theory of diffusion controlled reactions than that presented by Collins and Kimball. In particular, the investigators were interested in a more realistic formulation of the problem of high concentration quenching where quenches in the vicinity of...
Article
Solvent effects on the radiative transition probability (kF) of pyrene from S1 have been examined using an integrating sphere fluorimeter. The fraction of the total kF arising from the 00 band has been measured. The solvent effect on this quantity exactly parallels the extinction coefficient change for the 00 band with a rate of change in agreeme...
Article
Time-resolved fluorescence spectra were measured for pyrene and naphthalene adsorbed on a silica gel surface using the time-correlated photon-counting technique Excimer-Iike emission was observed within an excitation lamp duration of a few nanoseconds with both pyrene and naphthalene. It is suggested, from the excitation spectra, that ground state...
Article
The fluorescent lifetimes and relative fluorescent quantum yields of 9,10-dibromoanthracene solutions have been measured. It is found that the nonradiative transition rate of the lowest excited singlet of 9,10-dibromoanthracene is strongly dependent on the solvent and temperature, but is unaffected by the presence of heavy atoms in the solvent mole...
Article
A technique, based on the fast Fourier transform (FFT), for the deconvolution of fluorescence decay curves is proposed. To use this technique the exact functional form of the fluorescence decay law need not be assumed. The difficulties usually encountered with the Fourier transforms of noisy data are greatly reduced by choosing a limit v1 in the fr...
Article
Several methods of deconvoluting fluorescence decay curves are compared. Real data for which the decay times were known provide tests of each method's ability (1) to deconvolute two-component decays having decay times of 1 and 5 ns, (2) to cope with distortions in the data resulting from instrumental artifacts, (3) to analyze sub nanosecond decay t...
Article
Advantage has been taken of the measured pulse width of synchrotron radiation and its independence of wavelength to determine the delta-pulse response of a vacuum uv photomultiplier. This photomultiplier was then used to establish the true time profile of a nanosecond H(2) flashlamp. Two numerical techniques (the exponential series method and the f...
Article
Measurements have been made of the fluorescence lifetimes of several alkanes in the collision-free vapour state. The fluorescence lifetimes decreased with increasing energy of excitation, but the lifetimes of molecules excited near the zero point level exhibited values similar to the neat liquid values, indicating the absence of a very strong solve...
Article
For short lifetimes τ0 of a donor Ax, the linear expression between 1/ϕ and 1/(B), where ϕ is the quantum yield of diffusion-controlled sensitization and (B) the average concentration of the acceptor B, is no longer valid and a more accurate relation with non-stationary diffusional terms should be used.
Article
We propose a quantitative method for computing the time-dependent value of the apparent rate constant of a bimolecular reaction in the liquid phase in The model proposed permits one to determine the time-dependence of the apparent rate constant of a bimolecular process in the case where a competition The results are necessary for the understanding...
Article
In a previous paper (II in this series), we showed that the kinetic parameters of a partly diffusion controlled reaction could be calculated when the p Three examples of fluorescence quenching of electronically excited states were studied: pyrene by biacetyl; sulforhodamine G by I−; and POPOP by fluorescence and fluorescence polarization measuremen...
Article
The kinetic behavior of the exciplex formed between electronically excited α-cyanonaphthalene and ground-state 1,2-dimethylcyclopentene in nonpolar and slightly polar solvents is reported. Analysis of two-component fluorescence decay curves indicates that in each solvent exciplex formation and decay in general follow the simple "excimer-type" mecha...
Article
A study of the photokinetics of the quenching of carbazole by pyridine and 2,6-dimethylpyridine is reported. A set of rate constants has been obtained on the basis of the Mataga kinetic scheme for the reactions of hydrogen bond formation and decomposition in the excited state. Both steady-state and transient fluorescence experiments were carried ou...
Article
Static fluorescence measurements and laser flash photolysis experiments have permitted the elucidation of the mechanism of photocyclization of 1-(o-diphenyl)-1-phenylethylene (a 1,1-diarylethylene). By fluorescence measurements, the quantum yield and the lifetime of fluorescence are found to be φf = 0.09 and τf = 4 × 10-9 s-1, respectively. By flas...
Article
Analysis of decay curves of electronically excited molecules A* versus time in presence of quencher B leads to the determination of kinetic data for the reaction (i.e. for diffusion limited reactions, the experimental collisional distance σ′ greater than the true collisional distance σ) and the sum D of diffusion coefficients of both reactants). Ex...
Article
An instrument is described for measuring fluorescence lifetimes, fluorescence excitation spectra, and relative fluorescence quantum yields by photon counting in the vacuum ultraviolet. The temporal resolution is satisfactory down to lifetimes of 200 psec, and the sensitivity permits measurements on totally absorbing samples with quantum yields as l...
Article
The photokinetics of the fluorescence quenching of anthracene by N,N-dimethylaniline has been investigated by fluorescence decay and steady state techniques. It has been found that the transient effects associated with diffusion-controlled reactions must be taken into account. The forward reaction is diffusion controlled and the kinetic behavior of...
Article
The influence of diffusion on the excimer or exciplex photokinetics has been investigated by numerical integration of the standard coupled differential equations for the situation where the forward quenching step has a time-dependent rate constant given by the continuum theory of diffusion-controlled reactions. The influence of diffusion on both th...
Article
The forbidden 1B2u−1A1g(S1−S0) radiative transition probabilities for seven single vibronic levels (SVL) in 1B2u benzene vapor have been determined from new measurements of SVL fluorescence yields and lifetimes. New yields are also given for 17 other levels in C6H6 and 8 levels in C6D6. The radiative probabilities are each sums of many single chann...
Article
Relative band intensities have been measured in 13 strong progressions found in seven single vibronic level fluorescence spectra from benzene. Neither first nor second-order Herzberg-Teller theory can account for the band intensities in the strict harmonic approximation. The introduction of Fermi resonances involving levels separated by 121 cm-1 an...
Article
The photophysics of the interaction of α-cyanonaphthalene in its first excited singlet state with dimethylcyclopentene-1,2 as a quencher is reported over the temperature range of 0 to -40°C in hexane. In this temperature range the system exhibits the typical photokinetics of a feedback system with two-component monomer decay. From an analysis of th...
Article
Excitation of a series of aralkyl thiones into the S2 (π,π*) state leads to a formal insertion into the δ position and the formation of cyclopentyl thiols. Excitation into the S1 (n,π*) state does not lead to the same products and reaction is very slow. The former reaction may be quenched with biacetyl, but not with up to 2 M piperylene, nor can it...
Article
A new instrument intended for the measurement of relative fluorescence quantum yields is described. This instrument incorporates an integrating sphere to eliminate corrections due to polarization and to index of refraction phenomena. The primary standard was quinine bisulphate in 1 N H2SO4. Quantum yields are reported for quinine bisulphate (0.1 N...
Article
The oxygen quenching of pure liquid toluene has been investigated to examine departures from simple Stern–Volmer kinetics resulting from transient effects (diffusion control) and static quenching due to the presence of a contact ground state complex. Static quenching is easily observed when excitation is on the red edge of the absorption spectrum....
Article
A number of aralkyl thiones have been prepared all of which exhibit fluorescence from the higher singlet, S2, with the high quantum yield ΦF ≈ 5 × 10−3.
Article
A test of the continuum model for diffusion controlled reactions as applied to fluorescence quenching is presented and discussed. By proper selection of systems, it was possible to observe nonexponential decay which followed the decay law exp(−at − 2b√t) as predicted by the continuum model. Analysis of these decay curves gave the encounter radius a...

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