Relative Peak Height Research Articles

The magneto-optical and optical properties of ultrathin Fe films in the short-wavelength range

The magneto-optical and optical properties of ultrathin Fe films sandwiched between Au layers were studied. A pronounced Kerr rotation peak is observed respectively in the photon energy range of 3.6–3.8 eV when the Fe layer is thinner than 1.5 nm, and in the range of 3.4–3.5 eV for thicker Fe layers. In simple calculations, the Kerr rotation peak is demonstrated to originate from the variation of the off-diagonal element in dielectric tensor of the Fe layers. The relative peak height Δθk, the normalized Kerr rotation θkn, and the effective optical constants at the photon energy of 3.5 eV are found to oscillate as a function of dFe.

Excimer Model for Photoluminescence in Single-Crystal C60

We report the photoluminescence spectrum of well characterized, epitaxially grown single-crystal C60 thin films. The highly regular and reproducible spectral features observed can be explained by a simple molecular model which takes into account enhanced coupling of an excited C60 molecule with its nearest neighbor. This model provides an identification of all the observed spectral features at low temperature including a qualitative understanding of the relative peak height ratios, as well as the observed temperature dependence of the photoluminescence spectrum.

Detection of hypoglycemic drugs in human urine using micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) is evaluated as a potential analytical method for the separation and detection of a series of sulfonylurea drugs used in the treatment of hyperglycemia. These drugs are often surreptitiously abused, producing extremely low blood glucose levels and symptoms indistinguishable from those associated with an insulin-secreting tumor. Separation buffer containing 50 mM sodium dodecyl sulfate (SDS) was found to be adequate for the MEKC separation of the third generation drugs (glipizide and glyburide) but not the second generation drugs (acetohexamide chlorpropamide, tolazamide, and tolbutamide). At a pH of 8.5 in the presence of 20 mM borate/20 mM phosphate and 150 mM SDS, all seven components were adequately resolved with an analysis time of 17 min. Altering the concentration of the buffering components to either 5 mM borate/5 mM phosphate or 40 mM borate alone reduced the analysis time to less than 10 min with no observable loss in resolution. A series of other micelle-forming surfactants were evaluated, and only sodium cholate provided an improvement over the SDS-based system. Optimal separation was obtained with 75 mM sodium cholate and led to complete analysis with baseline resolution of all seven components in less than 8 min. These conditions were shown to be adequate for the detection of the hypoglycemic drugs spiked into normal urine and in patients taking these drugs. The precision associated with nine consecutive injections of six samples (n = 54) was found to be acceptable with percent coefficient of variance for absolute migration times (MTabs) for all peaks averaging 0.89 with peak area and peak height being 8.49 and 8.26, respectively. The between-sample precision was found to average 0.92% for MTabs and 8.56% and 8.45%, respectively, for the relative peak area and peak height. With a detection limit for the drugs in urine (following extraction) in the 50 ng/mL range, the potential exists for an MEKC-based assay for the detection of sulfonylurea drugs in urine.

Photoluminescence spectra of epitaxial single crystal C 60

We report the photoluminescence spectrum of well characterized, epitaxially grown single crystal C 60 thin films. The highly regular and reproducible spectral features observed can be explained by a simple molecular model which takes into account enhanced coupling of an excited C 60 molecule with its nearest neighbor. This model provides an identification of all the observed spectral features at low temperature including a qualitative understanding of the relative peak height ratios, as well as the observed temperature dependence of the PL spectrum.

Application of capillary and free-flow zone electrophoresis and isotachophoresis to the analysis and preparation of the synthetic tetrapeptide fragment of growth hormone-releasing peptide.

The use of high-performance electromigration separation methods, capillary zone electrophoresis (CZE) and capillary isotachophoresis (CITP) and continuous free-flow arrangements of these two separation principles, free-flow zone electrophoresis (FFZE) and free-flow isotachophoresis (FFITP), was investigated in the analysis and purification of the synthetic C-terminal tetrapeptide fragment (H2N-Ala-Trp-D-Phe-Lys.NH2) of the growth hormone-releasing peptide. CZE and CITP were used for microanalysis of peptide preparations after different steps of their purification. The homogeneity of the peptide preparations, including fractions of preparative separations, was quantified by relative zone length (CITP) and/or relative peak height (CZE). In addition, the data obtained by CZE and CITP (electrophoretic and electroosmotic flow migration velocities) were utilized for conversion of micro-scale capillary separations (nano- to picomole level) into the preparative separations realized by FFZE and FFITP with a capacity from tens to hundreds of milligrams per hour.

Protein denaturation in nonlinear isocratic and gradient elution chromatography

AbstractProtein denaturation, common in hydrophobic adsorption systems, causes misinterpretation of adsorption mechanisms, interferes with analysis in analytical chromatography, and complicates the design of large‐scale adsorption processes. A detailed adsorption model isolates the effects due to denaturation from those due to mass transfer and intrinsic adsorption kinetics. The model is verified using protein gradient elution data. Simulations establish that typical symptoms of denaturation in frontal and elution chromatogrrams include sensitivity to changes in feed composition, column length, particle size, and operating conditions (feed size, flow rate, and column history). When a denatured species adsorbs irreversibly, the elution chromatogram shows decreasing peak area with increasing incubation time and apparent adsorption hysteresis over repeated cycles. In gradient elution, the peak elution order, resolution, and relative peak height depend highly on modulator properties and operating conditions. Interfering species limit solid‐phase induced denaturation by competing for binding sites. Strategies for detecting and minimizing denaturation are proposed.

Interactions of model human pulmonary surfactants with a mixed phospholipid bilayer assembly: Raman spectroscopic studies.

The temperature dependence and acyl chain packing properties of the binary lipid mixtures of dipalmitoylphosphatidylcholine-d62 (DPPC-d62)/dipalmitoylphosphatidylglycerol (DPPG) multilayers, reconstituted with two synthetic peptides for modeling the membrane behavior of the SP-B protein associated with human pulmonary surfactant, were investigated by vibrational Raman spectroscopy. The synthetic peptides consisted of 21 amino acid residues representing repeating charged units of either lysine or aspartic acid separated by hydrophobic domains consisting of four leucines (KL4 or DL4, respectively). These peptides were designed to mimic the alternating hydrophobic and hydrophilic sequences defining the low molecular weight SP-B protein. Raman spectroscopic parameters consisting of integrated band intensities, line widths, and relative peak height intensity ratios were used to probe the bilayer order/disorder characteristics of the liposomal perturbations reflected by the reconstituted membrane assemblies. Temperature profiles derived from the various Raman intensity parameters for the 3100-2800-cm-1 carbon-hydrogen (C-H) and the 2000-2300-cm-1 carbon-deuterium (C-D) stretching mode regions, spectral intervals representative of acyl chain vibrations, reflected lipid reorganizations specific to peptide interactions with either the DPPC-d62 or DPPG component of the liposome. For the multilamellar surfactant systems composed of either KL4 or DL4 reconstituted with the binary DPPG/DPPC-d62 lipid mixture, the breadth of the gel to liquid crystalline phase transition temperatures TM, defined by acyl chain C-H and C-D stretching mode order/disorder parameters, increased from about 1 degree C in the peptide-free systems to over 10 degrees C. This breadth in TM indicates an increased lipid disorder and a distinct noncooperative chain melting process for the model liposomes. In comparing the interactions of the synthetic peptides with DPPG/DPPC mixtures and with DPPC liposomes alone, the negatively charged DL4 peptide perturbs the DPPG component of the lipid mixture more strongly than the DPPC-d62 component; moreover, the DL4 peptide disrupts the structure of the DPPG lipid domains in the binary mixture to a greater extent than the KL4 peptide. The microdomain heterogeneity of the binary lipid mixture arising from lipid-peptide interactions is discussed in terms of the Raman spectral properties of the multilayers. The Raman data in conjunction with previous bubble surfactometer and animal studies (Cochrane & Revak, 1991) suggest that lipid domain structures are present in functional surfactants and that the dynamic bilayer microheterogeneity induced by the surfactant peptide or protein is essential for pulmonary mechanics.

Location of rare-earth atoms in isomorphous series of complex oxides by employment of difference Fourier syntheses based on X-ray powder profile analysis: La3LnBaCu5O13+δ(Ln = Y, La, Nd or Gd) and LnBa2Cu3O7±δ(Ln = Y, Nd, Pr, Gd or Dy)

Analysis of the X-ray powder diffraction profiles of an isomorphous series of inorganic solids has been carried out for two series of complex oxides: $La_3LnBaCu_5O_{13+\delta} $(Ln = Y, Nd or Gd) and $LnBa_2Cu_3O_{7\pm\delta}$ (Ln = Y, Nd, Pr, Gd or Dy). In this method, profile and structure refinements of a reference compound are followed by a difference Fourier synthesis to locate the positional parameters of a substituent atom. A linear correlation exists between the Fourier peak height in the difference Fourier map and the atomic number of the substituent atom. By an analysis of relative peak height in the correlation plot, the extent of cation disorder, if any, can be determined.

Differential molecular dynamics and transmembrane fluidity gradients in canine myocardial sarcolemma and sarcoplasmic reticulum

The molecular dynamics of highly purified preparations of canine myocardial sarcolemma (SL) and sarcoplasmic reticulum (SR) were quantified by electron spin resonance spectroscopy (ESR). Canine myocardial SL and SR have substantially different motional regimes in their membrane interiors as demonstrated by alterations in the relative peak height ratios, peak widths and peak splittings in ESR spectra of 16-doxylstearate incorporated into SL and SR. Quantification of the apparent order parameters (S) of 16-doxylstearate in SL and SR by analyses of ESR spectra demonstrated that the interior of the SL membrane was substantially more immobilized than the interior of the SR membrane (e.g. S = 0.168 ± 0.002 for SL and S = 0.128 ± 0.003 for SR). In contrast, only modest differences in membrane dynamics near the hydrophobic-hydrophilic interface were present in SL and SR as ascertained by ESR spectra of the probe 5-doxylstearate incorporated into these membranes. Myocardial sarcolemma contained heretofore unsuspected amounts of cholesterol (1.4 ± 0.1 μmol cholesterol/mg protein) while sarcoplasmic reticulum contained only small amounts of cholesterol (0.17 ± 0.06 μmol cholesterol/mg protein). Model systems employing binary mixtures of plasmenylcholine/cholesterol and phosphatidylcholine/cholesterol demonstrated that the observed alterations in molecular dynamics were due, in large part, to the differential cholesterol content in these two subcellular membrane compartments. Taken together, these results demonstrate that these two functionally distinct myocardial subcellular membranes have markedly disparate molecular dynamics and transmembrane fluidity gradients which may facilitate their performance of specific functional roles during excitation-contraction coupling in myocardium.

A single-fluor approach to DNA sequence determination using high performance capillary electrophoresis.

The Tabor and Richardson strategy for enzymatic chain termination sequencing of DNA using relative peak intensity has been adapted to high performance capillary gel electrophoresis with laser induced fluorescence detection. This approach to DNA sequencing involves the use of only a single fluor and results in significant reduction in the time required to determine a DNA sequence without the use of highly complicated and expensive instrumentation. We present a modification of the Tabor and Richardson approach employing two reactions, each containing complementary mixtures of only three ddNTP's in the concentration ratio 4:2:1. The DNA sequence is determined by relative peak height and by assigning the missing ddNTP to "gaps" between the peaks. The use of only three terminators/reaction simplifies the software task of differentiating between the termination types and makes more efficient use of the available dynamic range. Both complementary mixes generate complete sequence information and the two data files are combined in order to make a more confident sequence call. This process helps to eliminate errors caused by occasional non-uniform incorporation of ddNTP's or false terminations and also alleviates some of the difficulty associated with reading through compressed regions of the electropherogram.

Raman spectroscopic studies of model human pulmonary surfactant systems: phospholipid interactions with peptide paradigms for the surfactant protein SP-B

The temperature dependence of dipalmitoylphosphatidylcholine (DPPC)/phosphatidylglycerol (PG) multilayers, reconstituted with various synthetic peptides for modeling human lung surfactant, was monitored by vibrational Raman spectroscopy. The synthetic peptides consisted, respectively, of residues 59-81 of the human surfactant protein SP-B and 21 amino acid residue peptides containing repeating units of arginine separated by either four or eight leucines (RL4 or RL8). Each peptide demonstrated the ability to reduce significantly the surface tension of analogues of the phospholipid mixture used in the Raman studies. Raman spectroscopic integrated band intensities and relative peak height intensity ratios, two spectral parameters used to determine bilayer disorder, provided sensitive probes for characterizing multilayer perturbations in the reconstituted liposomes. Temperature profiles derived from the various Raman intensity parameters for the 3100-2800-cm-1 carbon-hydrogen (C-H) stretching mode region, a spectral interval representative of acyl chain vibrations, reflected lipid reorganizations due to the bilayer interactions of these peptides. For the three reconstituted multilamellar surfactant systems, the gel-to-liquid-crystalline phase-transition temperatures Tm, defined by acyl chain C-H stretching mode order/disorder parameters, increased from 35 degrees C in the peptide free system to 37-38 degrees C, indicating increased lipid headgroup constraints for the model liposomes. Although the values of Tm were similar for the three recombinant lipid/peptide assemblies, individual phase-transition cooperativities varied significantly between systems and between spectroscopically derived order/disorder parameters.

Raman spectroscopic studies of dimyristoylphosphatidic acid and its interactions with ferricytochrome c in cationic binary and ternary lipid-protein complexes

The vibrational Raman spectra of both pure 1-alpha-dimyristoylphosphatidic acid (DMPA) liposomes and DMPA multilayers reconstituted with ferricytochrome c at pH 7 and pH 4, with either sodium or calcium as the cation, are reported as a function of temperature. Multilayers composed of a 1:1 mol ratio DMPA and dimyristoylphosphatidylcholine with perdeuterated acyl chains (DMPC-d54) have also been reconstituted with approximately 10(-4) M ferricytochrome c for Raman spectroscopic observation. Total integrated band intensities and relative peak height intensity ratios, two spectral Raman scattering parameters used to characterize bilayer properties, are sensitive to the presence of both ferricytochrome c and the cation in the reconstituted liposomes. Temperature profiles, derived from the various Raman intensity parameters for the 3,100-2,800 cm-1 lipid acyl chain C-H stretching mode region specifically reflect bilayer perturbations due to the interactions of ferricytochrome c. At pH 4 the calcium DMPA multilamellar gel to liquid crystalline phase transition temperatures Tm, defined by either the C-H stretching mode I2850/I2880 and I2935/I2880 peak height intensity ratios, are 58.5 +/- 0.5 degrees C and 60.0 +/- 0.3 degrees C, respectively. This difference in Tm's resolves the phase transition process into first an expansion of the lipid lattice and then a melting of the lipid acyl chains. At pH 7 the calcium DMPA liposomes show no distinct phase transition characteristics below 75 degrees C. For sodium DMPA liposomes reconstituted with ferricytochrome c at either pH 4.0 or pH 7.0, spontaneous Raman spectra show altered lipid structures at temperatures above 40 degrees C. Resonance Raman spectra indicate that ferricytochrome c reconstituted in either calcium or sodium DMPA liposomes changes irreversibly above Tm. For either the binary lipid or ternary lipid-protein systems reconstituted with DMPC-d54, linewidth parameters of the DMPC-d54 acyl chain CD2 symmetric stretching modes at 2,103 cm-1 provide a sensitive measure of the conformational and dynamic properties of the perdeuterated lipid component, while the 3,000 cm-1 C-H spectral region reflects the bilayer characteristics of the DMPA species in the complex. Although calcium clearly induces a lateral phase separation in the DMPA/DMPC-d54 system at pH 7.5 (Kouaouci, R., J.R. Silvius, I. Grah, and M. Pezolet. 1985. Biochemistry. 24:7132-7140), no distinct lateral segregation of the lipid components is observed in the mixed DMPA/DMPC-d54 lipid system in the presence of either ferricytochrome c or the sodium and calcium cations at pH 4.0. However, domain formation, consisting of regions rich in DMPA and DMPC-d54, respectively, is suggested for the calcium binary lipid mixture at pH 4.0 by the different values for Tm and AT characterizing the DMPA and DMPC-d54 species.Spectral evidence strongly suggests that ferricytochrome c also induces domain formation in the ternary lipid-protein mixtures at pH 7.0, but only for the sodium cation.

Oxygen substitution in sputter-deposited MoS 2 films studied by extended X-ray absorption fine structure, X-ray photoelectron spectroscopy and X-ray diffraction

The morphology and crystallite structure/orientation of sputter-deposited MoS 2 solid lubricant films have been shown to be strongly affected by oxygen-containing species in the sputtering chamber. We have studied the effect of oxygen incorporation within these films using extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Films produced at The Aerospace Corporation, the National Centre of Tribology (U.K.), Hohman Plating and Manufacturing, and NASA Lewis Research Center were studied to determine common characteristics of different MoS 2 films produced by sputter deposition. In agreement with previous results, XPS of the films indicated a bulk anion:cation ratio ( i.e. (S+O):Mo) of about 2, and XRD revealed that the films consisted completely of MoS 2-like phases that were compressed in the ( h k 0) directions as compared with pure MoS 2. This “edge plane compression” appeared to correlate with oxygen content. EXAFS confirmed the absence of MoO 2 in the films and indicated that the films actually consist of two similar MoS 2-like phases. Correlation of the EXAFS results with those obtained from XPS and XRD indicated that the two phases are MoS 2 and an MoS 2- x O x substitutional solution. The solid solution may be described as MoS 2 with oxygen atoms that have substituted for sulfur atoms in the MoS 2 crystal lattice. Relative peak height changes in the EXAFS radial distribution curves indicated that increasing amounts of oxygen cause a reduction in the size of crystallites in the films. The presence of the MoS 2- x O x phase may explain the superior tribological performance of MoS 2 films in some applications, which has been shown to correlate with oxygen impurities in the films.

Elimination of z-ejection in Fourier-transform ion cyclotron resonance mass spectrometry by radio/frequency electric field shimming

In Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometry, coherent ion cyclotron orbital motion is produced by resonant radio frequency (rf) electric field excitation. However, because the excitation electrodes are of finite dimensions, the desired transverse (to the applied magnetic field) rf electric field is accompanied by an rf electric field component along the z- (magnetic field) direction, resulting in mass-dependent z-ejection and mass-dependent FT/ICR mass spectral peak relative magnitudes. Addition of several "guard wires" of voltage-divided rf amplitude allows the rf electric field to be "shimmed" to near-perfect uniformity. In this paper (see also the accompanying paper by Russell et al.), we introduce two types of rf-shimmed ion traps. In the first type, guard wires are placed only in front of the trapping electrodes. In the second type, guard wire rings are placed inside the detector and trapping electrodes. For either arrangement, simion simulations were used to adjust the rf voltages applied (by use of voltage dividers) to the guard wires or rings so as to produce an optimally uniform rf field within the trap. The virtual elimination of z-excitation is confirmed by plots of magnitude-mode relative peak height vs ICR orbital radius. Because the guard wires (or rings) tend to shield the ions from the trapping electrode potential, the shift in ICR frequency with trapping voltage is also reduced, but not as well as by a screened trap.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the application of thin layer isoelectric focusing to food analysis. III. Identification of mushroom by numerical value of isoelectric focusing pattern and application to food poisoning by Rhodophyllus rhodopolius.

To identify the species of mushrooms mainly for the distinction of poisonous mushrooms from edible ones, thin layer isoelectric focusing analysis was applied on their water-soluble proteins. 1. The electrophoretic profiles were species-specific. The proteins extracted from the cap and stem in a species gave essentially identical profiles. 2. The profiles of cap proteins of 10 individuals of Akamomitake (Lactarius deliciosus) were indifferent, indicating that the intra-species variation of water-soluble proteins was little. 3. The heat treatment at higher than 60°C, for 10 min, of the water-soluble proteins of Dokutsurutake (Amanita virosa) caused temperature-dependent disappearance of protein bands, while not significant change up to 60°C. 4. The values of pI and relative peak height of isoelectro-focused water-soluble protein bands were numerically expressed. These numerical values were species-specific, indicating that mushroom species might be identified by analyzing the water-soluble proteins with a verification of the tables of these numerical values. 5. The present method was applied for the identification of poisonous Kusaurabenitake (Rhodophyllus rhodopolius) mixed in Urabenihoteishimeji (Rhodophyllus crassipes) which caused a food poisoning incident. The former mushroom was satisfactorily identified by this method.

Interaction of ferricytochrome c with zwitterionic phospholipid bilayers: a Raman spectroscopic study.

The vibrational Raman spectra of both pure L-alpha-dipalmitoylphosphatidylcholine (DPPC) liposomes and DPPC multilayers reconstituted with ferricytochrome c under varying conditions of pH and ionic strength are reported as a function of temperature. Total integrated band intensities and relative peak height intensity ratios, two spectral scattering parameters used to determine bilayer disorder, are invariant to changes in pH and ionic strength but exhibit a sensitivity to the bilayer concentration of the ferricytochrome c. Protein concentrations were estimated by comparing the 1636 cm-1 resonance Raman line of known ferricytochrome c solutions to intensity values for the reconstituted multilayer samples. Temperature-dependent profiles of the 3100-2800 cm-1 C-H stretching, 1150-1000 cm-1 C-C stretching, 1440 cm-1 CH2 deformation, and 1295 cm-1 CH2 twisting mode regions characteristic of acyl chain vibrations reflect bilayer perturbations due to the weak interactions of ferricytochrome c. The DPPC multilamellar gel to liquid-crystalline phase transition temperature, TM, defined by either the C-H stretching mode I2935/I2880 or the C-C stretching mode I1061/I1090 peak height intensity ratios, is decreased by approximately 4 degrees C for the approximately 10(-4) M ferricytochrome c reconstituted DPPC liposomes. Other spectral features, such as the increase in the 2935 cm-1 C-H stretching mode region and the enhancement of higher frequency CH2 twisting modes, which arise in bilayers containing approximately 10(-4) M protein, are interpreted in terms of protein penetration into the hydrophobic region of the bilayer.

High pressure infrared spectroscopy of lipid bilayers: new tests for interdigitation

High-pressure infrared spectroscopy is used to compare the barotropic behaviour of various interdigitated lipid bilayer systems (1,2-di- O-hexadecyl- sn-glycero-3-phosphocholine, 1,3-dipalmitoyl- sn-glycero-2-phosphocholine and 1-palmitoyl- sn-glycero-3-phosphocholine) with non-interdigitated bilayers of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine. In the pressure range between 0 and 20 kbar, we have monitored the pressure dependence of the relative peak height intensity ratio of the chain methylene scissoring band, δCH 2, and its correlation field component band, δ′CH 2. We demonstrate that this parameter, in conjunction with a visual inspection of the pressure-induced correlation field splittings of the methylene scissoring and rocking mode bands, can provide reliable indications of chain interdigitation.

A Temperature Dependence Study of 35Cl Nuclear Quadrupole Resonance Frequencies in Some Hexachloroplatinate(IV) Hexahydrates

The temperature dependence of 35Cl NQR frequencies was investigated in various hexachloroplatinate( IV) hexahydrates containing the following divalent ions as counter cations: Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Ba(II). All of the compounds except the Cu(II) and Ba(II) salts yield a single 35Cl NQR line at all temperatures studied. For the Mn(II), Cu(II), and Ba(II) salts, the NQR frequencies are considerably shifted by deuteration. For the deuterated Mn(II) salt, two 35Cl NQR lines were observed whose relative peak-height intensities vary in dependence on the history of the thermal treatment of the sample. The very broad higher frequency line could be observed for a sample which had been at 77 K or below. It could not be observed for a sample which was cooled slowly to room temperature after it had been heated up to ca. 420 K. A structural phase transition was located at 135.6 and 129.4 K for the Cu(II) salt and its deuterated analog, respectively. The frequency shift by deuteration is discussed in relation to the strength of O - H ... CI type hydrogen bonds.

Micro high performance liquid chromatography of aliphatic amines by means of resonance raman detection

AbstractA micro high performance liquid chromatography coupled with a resonance Raman detection system is described. For highly sensitive Raman detection, aliphatic amines were derivatized with dabsyl chloride (4‐dimethylaminoazobenzene‐4′‐sulfonyl chloride). The derivatives were separated on an ODS micro column (0.5 mm i.d. × 145 mm PTFE tube). Chromatograms were obtained by measuring the intensity of Raman scattering at 1136 cm−1 with the 488.0 nm line of an Arion laser. The lower detection limit was 1.5 ng and the RSD of relative peak height (n = 9) was 5.9% at 11 ng of methylamine derivative. Moreover, by stopping the flow of the micro HPLC system at the retention time of the individual derivatives, it was possible to measure their resonance Raman spectra.

Evaluation of a Fourier-Transform-Based Pattern-Recognition Algorithm for Two-Dimensional Fluorescence Data

A pattern-recognition algorithm for two-dimensional fluorescence data previously reported is critically evaluated. The three spectral matching criteria—sum of the absolute value of the imaginary coefficients of the frequency-domain correlation function, sum of the absolute value of the real-negative coefficients of the frequency-domain correlation function, and the intervector distance between the abbreviated Fourier transforms of two spectra—are calculated. Spectra simulated with a computer as well as data acquired with a video fluorometer are examined. Results indicate that all three parameters are sensitive to changes in peak position, peak width, relative peak height, and intensity of background noises.