In this study we investigate visible fluorescence of cytotoxic bio-markers (molecular probes) based on the
derivatives of piperidone at femtosecond infrared pulsed laser excitation. The subject of this investigation is
the origin of the fluorescence. Does it originate from the excited state absorption, which occurs only at
slow, nanosecond excitation, or is it due to intrinsic multi-photon absorption? In the past, it has been
shown indirectly, through the laser photolysis study, that the contribution of the excited state absorption is
minimal for several compounds of such type. The results of direct experiments with an infrared
femtosecond fiber laser as an excitation source described here support this hypothesis. The observed
dependence of the fluorescence on the pump power indicated the contribution of not only two-photon, but
multi-photon routes of excitation. Additionally, it was shown that the spectral features of the fluorescence
correlate with the presence of glycine, an amino acid that is one of the building blocks of proteins in a cell.
The implication of this result is, in addition to their anticancer action, the compounds can possibly be used
for fluorescent diagnostics of cancer and multi-photon fluorescent microscopy of malignant cell cultures
using portable infrared fiber lasers as excitation sources.
We present the results of our investigation of new derivatives of cyclohexanone and piperidone compounds that have exhibited in the past anticancer effect due to biochemical destruction of cancer cells. In this study we focus on using these compounds as markers for malignant cells because of their strong two-photon excited fluorescence. Their molecular cross-section of two-photon absorption can be as high as 3000x10-50cm4s/photon and compares well with Rhodamine B, well-known fluorescent molecular probe. This provides an option for monitoring the biochemical destruction of cancer cells by means of two-photon excited fluorescence spectroscopy. Initially we studied the two-photon fluorescence of the solutions of pure compounds. Then we mixed the compounds with amino acids (Glycine and Alanine), the major building blocks of proteins in cells, hoping that the fluorescence will give some insight in the interaction between the compounds and bio substances. We discuss the solubility issues, the cross-section of twophoton absorption of the compounds, and also the features of the spectrum of the two-photon excited fluorescence. Compounds combining both properties (cytotoxicity and two-photon excited fluorescence), which are now carried by different chemical agents, are expected to improve the efficiency of cancer treatment and lower the cost.
Potassium dihydrogen phosphate KDP; (KH2PO4) and triglycine sulfate TGS; (CH2NH2COOH.H2SO4), are extensively studied ferroelectric materials, and find wide applications in electrooptic and infrared detecting devices respectively. L-arginine phosphate monohydrate (C6H14N4O2H3PO4.H2O), abbreviated as LAP, is a highly transparent monoclinic crystal with attractive properties for efficient frequency conversion of infrared lasers. Effects of doping KDP and TGS crystals with LAP are investigated. It was found in both cases that LAP affects the growth morphology and other properties. The properties of resulting crystals in terms of growth morphology, optical and mechanical properties are presented and discussed.
Among the atmospheric properties that adversely affect laser propagation is air turbulence. One common optical parameter of air turbulence is the refractive index structure constant that quantifies the fluctuations in the refractive index caused by temperature fluctuations and hence air density fluctuations. There is a reason to believe, from theory and from sparse data that, when propagation occurs under widespread cloudy conditions, the refractive index structure constant is significantly reduced. Therefore the intensity of a propagating laser beam will not be degraded nearly as much as would be expected under clear or lightly scattered cloud conditions. New experimental data will be presented that support this hypothesis. The refractive index structure constant was measured for various cloud-cover conditions during daytime with additional factors present, such as changing crosswinds and precipitation. It was possible to observe the apparent pattern of the decrease of the refractive index structure constant by two orders of magnitude during the periods of increasing cloud-cover evaluated by the measurement of solar irradiance. The statistical correlation coefficient between the log of solar irradiance and the log of the refractive index structure constant was found to be around 0.9 (the closer it is to the maximum of 1.0, the stronger the correlation). The measurements were conducted with a commercial scintillometer/anemometer (1 m above ground, 500-m optical path length) in Northern Alabama in late spring and summer. The effect is believed to be due to the reduction of solar radiation, which caused the temperature gradient that initiated convection in the air. The results of this work can find their application in designing free space laser communication systems and military laser systems.
Distribution A. Approved for public release; distribution unlimited. 1 Sep 04
This study explores the feasibility of using cytotoxic derivatives of cyclohexanone/piperidone with strong two-photon absorption (TPA) simultaneously for fluorescent labeling of cancer cells and their subsequent biochemical destruction. Recent studies have shown that these compounds have an efficient two-photon excited fluorescence when pumped with infrared laser radiation. Their molecular cross-section of TPA can be as high as 30.0x10-48cm4s/photon. A cytotoxic two-photon absorbing compound will attach itself selectively to cancer cells and act as a fluorescent label of the cancer cell at harmless levels of excited infrared radiation. Also, when the process of chemical destruction of the cancer cell is over, the fluorescence changes its rate and optical spectrum. In this case, fluorescent labeling could yield more accurate information, not only on the location and distribution of cancer cells, but also on their evolution in time. Compounds combining both properties (cytotoxicity and two-photon excited fluorescence), which are now carried by different chemical agents, are expected to improve the efficiency of the cancer treatment and lower the cost.
The growth, synthesis and characteristics of a new organic nonlinear optical crystal, a derivative of Schiff base compounds, 4-nitrobenzylidene-4-chloroaniline are reported. Good-quality crystals have been successfully grown using Bridgman-Stockbarger (BS) Technique. The organic crystal, 4-nitrobenzylidene-4-chloroaniline, shows good second harmonic generation of 1.064 micron wavelength. A recent work done on the semiorganic nonlinear crystals are reviewed along with results of growth of a few L-arginine phosphate type crystals is presented.
A detailed study was conducted for two-photon absorption of a selected group of new derivatives of cyclohexanone/piperidone with regard to their molecular structure and the feasibility of using these derivatives as nonlinear optical absorbers for optical limiting. Derivatives of cyclohexanone/piperidone have a cross-section of two-photon absorption of the order of 3000 x 10-50cm4s/photon and compare well against known two-photon absorbers. This makes them promising nonlinear optical absorbers and optical limiters. Their important feature is that the energy is absorbed in the infrared region, where the protection is needed for remote IR sensors and night-vision systems. It is also important that the energy of the dissipated infrared radiation is converted mostly into fluorescence but not into heat that can damage optical limiter.