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PubMed2003

Binding of fullerene C60 to gold surface functionalized by self-assembled monolayers of 8-amino-1-octane thiol: a structure elucidation.

The formation of self-assembled chemisorbed monolayers (SAM) of 8-amino-1-undecane thiol functionalized with fullerene C(60) on gold, has been studied by contact angle measurements, Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A two-step procedure was followed consisting of the chemisorption of amine-terminated organosulfur compounds, followed by their reaction with fullerenes at the solid-liquid interface. Covalent binding of fullerenes to these attachment layers was accessed by FTIR-ATR and XPS. ATR showed several major features in the C(60) skeleton ring vibration region along with all the characteristic features of the aminothiol. With increase in carbon to sulfur ratio, appearance of a C1s shake-up satellite peak due to the characteristic pi-pi(*) transition of the C(60) backbone and a low binding energy N1s feature confirmed the z.sbnd;NH(2) binding at the 6,6 double bond of the C(60) cage. Possible explanations for these experimental findings are discussed.

Journal Article↗
PubMed1998

FTIR/ATR for protein adsorption to biomaterial surfaces.

It is now well accepted that the initial rapid adsorption of blood proteins to biomaterial surfaces is important in the long-term performance of the implant. Cells that interact with the implant will be reacting to a layer (single or multiple) of adsorbed protein. The parameters of importance in a study of protein adsorption to surfaces of biomaterial interest include total amounts of different adsorbed proteins and the conformation and orientation of these adsorbed proteins. Researchers have developed a number of techniques with which we can now address all these questions. In this paper, we have discussed how Fourier transform infrared (FTIR) attenuated total internal reflection (ATR) techniques can be used for the study of biomaterial surfaces and events at biomaterial surfaces such as protein adsorption. FTIR spectroscopy offers higher signal-to-noise and speeds than spectrometers that use gratings and hence offers the capability of observing the critical early events when proteins interact with surfaces. Perhaps the biggest advantage of the FTIR technique over dispersive spectrometers is wavelength precision. This allows the subtraction of water, a strong infrared absorber, from the spectra of proteins in aqueous solutions. This review starts with an introduction of how ATR can be used to provide information about proteins on surfaces. Equations to calculate the amount of proteins adsorbed to surfaces from analysis of ATR spectra are presented. A discussion of the kinds of surfaces that can be analyzed by FTIR/ATR and difficulties with the subtraction of H2O is given. The rest of the review deals with how information of interest to biomaterials researchers such as kinetics of protein adsorption, changes in protein secondary structure and orientation upon adsorption to surfaces can be obtained by FTIR/ATR.

Adsorption↗
PubMed2001

The use of thiamine and thiamine antagonists to investigate the etiology of early mortality syndrome in lake trout (Salvelinus namaycush).

Early mortality syndrome (EMS) is a non-infectious disease affecting lake trout and other salmonids in the Great Lakes and in inland lakes. It is characterised by loss of equilibrium, hyperexcitability, anorexia, and eventually death. EMS is associated with low thiamine and treatment of eggs or fry with thiamine-HCl eliminates symptoms and mortality. To verify the role of the active form of the vitamin as the prophylactic agent, we used thiamine pyrophosphate (TPP) to reverse EMS symptoms. We also investigated the ability of specific thiamine antagonists that either block TPP production or interfere with its function to induce EMS. When graded doses of TPP were administered to EMS-susceptible sac-fry, there was a dose-dependent reduction in EMS. The egg concentration of TPP that was associated with reduced EMS was similar to the threshold thiamine concentration found in feral lake trout stocks where EMS occurs. A thiamine deficient stock from Lake Ontario was very sensitive to the thiamine antagonist oxythiamine (OXY) with total mortality associated with developmental arrest occurring at an antagonist to thiamine molar ratio (ATR) above 7:1. The threshold ATR with OXY for development of EMS-like neurological signs in this stock was 1.6:1. In addition to EMS-like neurological signs, OXY caused dose-dependent increases in hydrocephalus, developmental arrest, and vitelline congestion in the Lake Ontario stock. These signs are consistent with those observed in feral fish exhibiting EMS. Much higher doses of antagonists were required (both pyrithiamine (PT) and OXY) to induce EMS-like clinical signs in the thiamine replete Lake Manitou stock. PT was a more potent inducer in this stock as the ATR associated with development of clinical signs was 111:1 for PT compared with 892:1 for OXY. These data provide experimental evidence supporting the hypothesis that a thiamine deficiency in the natural environment is the cause of EMS.

Animals↗
PubMed2000

FT-IR microspectroscopy for microbiological studies.

In this article we present an infrared microspectroscopic investigation on Candida albicans microcolonies, taken as a model system for studies on other microorganisms. Excellent Fourier transform infrared (FT-IR) absorption spectra from 4000 to 850 cm(-1) have been collected in only 20 s from sampling areas of 100x100 microm(2) in microcolonies, which had been transferred from the agar plate onto zinc selenide (ZnSe) windows. When different regions within a single microcolony were investigated, absorption spectra with important differences in the carbohydrate absorption (from 1200 to 850 cm(-1)) were detected for the cells in the center and in the periphery of the colony. Results obtained on microcolonies grown on solid agar with increasing dextrose concentrations indicated that the observed spectral heterogeneity was related to differences in dextrose uptake, which was lower for the old cells in the center of the colony than for the metabolically active cells at the periphery. Although it is otherwise difficult to quantitatively evaluate the dextrose uptake in a microcolony, FT-IR absorption microspectroscopy offers a new and rapid method for the analysis of this process. The possibility of studying highly absorbing colonies by attenuated total reflection (ATR) by means of an ATR microscope germanium objective is also presented here for the first time. An evaluation of the contact area sampled by this technique is reported with a discussion of the spatial resolution, the quality and the potential of the ATR measurements.

Candida albicans↗
PubMed1997

Normal values of patellar and ankle tendon reflex latencies.

The clinical value of latency measurement of tendon reflexes in neurological patients has been reported by several authors. However, normal values are not readily comparable. In the present study, latencies and amplitudes of patellar (PTR) and ankle tendon reflexes (ATR) were measured at rest and after facilitation in 102 normal controls. A manually operated reflex hammer, tipped with electrically conductive rubber, ensured an immediate start of the sweep of the oscilloscope. Latencies showed a significant correlation with height (r = 0.70 for PTR and r = 0.72 for ATR, P < 0.0001) and to a lesser degree with age (r = 0.16 and r = 0.30, P < 0.0001). While amplitudes were highly variable, rendering them less useful for diagnostic purposes, latencies showed minimal intra-individual variability (CV 1.5 and 0.8%, respectively). Correlation of ATR-latency with the H-reflex latency of the soleus muscle was very high (r = 0.97, P < 0.0001). Comparison with three other hammer types yielded corresponding results with a hammer supplied with a piezo-electric element; however, significantly shorter latencies were found with a hammer with a microswitch, and with another hammer with a spring-contact, due to a delay from the tap on the tendon until the start of the sweep of the monitor.

Adult↗
PubMed2000

Isolation and characterization of copia-type retrotransposons in Arabidopsis thaliana.

We isolated two copia-type retrotransposons from Arabidopsis thaliana. We named these elements AtRE1 (Arabidopsis thaliana Retro Element 1) and AtRE2. Nucleotide sequence analysis revealed that both elements have long terminal repeats (LTRs), and that their internal sequences include one large open reading frame that could encode Gag protein, protease, integrase, reverse transcriptase, and RNaseH. The deduced amino acids sequences contain several domains that are conserved among a large family of retrotransposons. The primer binding site for first-strand DNA synthesis and the polypurine tract for second-strand DNA synthesis existed at corresponding positions. A 5bp target site duplication (TSD) sequence was also found in the flanking region of LTRs. Southern hybridization and sequence determination of the flanking region demonstrated that AtREs exist at different loci in the two A. thaliana ecotypes Columbia and Landsberg erecta. Moreover, AtRE2 exists at two loci in Landsberg erecta, in contrast to the existence of only one copy in Columbia. These findings suggest that AtREs were recently transfected via some mediators or that AtREs were transposed after differentiation of the two ecotypes. One cDNA clone derived from the transcripts of AtRE1 was isolated, and the nucleotide sequence showed that this RNA was transcribed in the antisense direction. RT-PCR analysis revealed that AtRE1 was transcribed in both directions. This result suggests that the antisense RNA controls the expression of AtRE1 at the post-transcriptional level.

Amino Acid Sequence↗
PubMed1998

Rapid determination of trans-fatty acids in human adipose tissue. Comparison of attenuated total reflection infrared spectroscopy and gas chromatography.

A rapid attenuated total reflection (ATR) infrared (IR) spectroscopy procedure was used for quantitating the levels of total trans-fatty acid methyl ester (FAME) derivatives in neat (without solvent) test samples isolated from human adipose tissue. This procedure requires no weighing of the laboratory sample. The single-beam spectrum of the trans-containing FAMEs was 'ratioed' against that of a reference material having only cis double bonds in order to obtain a symmetric absorption band at 966 cm(-1) on a horizontal background. A single-reflection ATR diamond cell that requires only about 1 microl of neat FAMEs was used. The average level of trans-fatty acids in human adipose tissue found by ATR (3.07+/-0.27%) was generally higher than that obtained by gas chromatography (2.59+/-0.20%). Reasons for such a difference are discussed.

Adipose Tissue↗
PubMed2000

Early unilateral auditory deprivation increases 2-deoxyglucose uptake in contralateral auditory cortex of juvenile Mongolian gerbils.

The effects of early onset, unilateral conductive hearing loss on tone-induced 2-deoxyglucose (2-DG) uptake in the auditory cortex of juvenile Mongolian gerbils (Meriones unguiculatus) were studied. Atresia of the left ear canal was induced at postnatal day 9 (P9) to achieve reversible auditory deprivation prior to onset of hearing (around P12). Atresia either persisted (ATR, n=4) or the canal was opened 15 min before the 2-DG experiments (RE, n=4) at P27. Control animals were either non-deprived (CON, n=4), or their left ears were plugged acutely (PAX, n=4). In PAX, 2-DG uptake in primary auditory cortex (AI) and anterior auditory field (AAF) was lower in right than in left AI and AAF. In contrast, in ATR and RE, uptake was significantly higher on the right side contralateral to the atresia. Hence, atresia during early development leads to plastic changes resulting in an interhemispheric imbalance of functional metabolism in favor of the auditory cortex contralateral to the manipulated ear. Distances between tone-induced 2-DG labeling in AI and AAF were increased in PAX, but smaller in ATR in the right compared to the left hemisphere, suggesting effects of atresia also on spatial relations in cortical tonotopic maps.

Acoustic Stimulation↗
PubMed1997

Spectroscopic identification of an amorphous-to-crystalline drug transition in a solid dispersion SCH 48461 capsule formulation.

Changes in the dissolution of a solid dispersion capsule formulation composed of amorphous SCH 48461 in a polyethylene glycol 8000 matrix were investigated. SCH 48461 [(3R,4S)-1,4-bis(4-methoxyphenyl)-3-(3-phenylpropyl)-2-azetidinone] is a potent cholesterol absorption inhibitor with low water solubility and low melting point. Several capsule lots placed under controlled storage conditions exhibited a slowing of dissolution as a function of time with large inter-lot and intra-lot dissolution variations. Capsule contents were analyzed by attenuated total reflectance infrared (ATR-IR) microspectroscopy and solid-state cross-polarization, magic angle spinning (CPMAS) 13C-nuclear magnetic resonance (NMR) spectrometry. ATR-IR microspectroscopic analysis showed large IR spectral differences between the lots including the presence of a crystalline drug fraction in lots which exhibited incomplete dissolution. Solid-state CPMAS 13C-NMR analysis confirmed the presence of a crystalline drug fraction in the problematic capsule lots. Both ATR-IR and CPMAS 13C-NMR spectral results produced a rank ordering of the crystalline drug fraction present in the capsule lots that correspond to the dissolution results.

Anticholesteremic Agents↗
PubMed2004

Astigmatism outcomes of horizontal temporal versus nasal clear corneal incision cataract surgery.

PURPOSE: To compare the short- and long-term astigmatism outcomes after cataract surgery using temporal clear horizontal corneal incisions and nasal horizontal clear corneal incisions. SETTING: Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, Maryland, USA. METHODS: This retrospective study included a consecutive series of eyes having phacoemulsification with implantation of a 6.0 mm foldable acrylic intraocular lens through a 3.5 mm horizontal clear corneal incision at 180 degrees (temporal incision in right eyes, nasal incision in left eyes). Astigmatism was measured by keratometry readings before surgery and 6 weeks and 12 months postoperatively. RESULTS: The mean preoperative astigmatism in the 178 eyes (94 right, 84 left) of 161 patients was 0.78 diopter (D); 54.5% of eyes had against-the-rule (ATR) astigmatism, 22.5% had with-the-rule (WTR) astigmatism, and 14.0% were astigmatically neutral. A significant shift toward WTR astigmatism occurred postoperatively. At 6 weeks, 48.3% of eyes had WTR astigmatism and 23.0% had ATR astigmatism. At 12 months, 43.8% had WTR astigmatism and 25.8% had ATR astigmatism. Vector analysis revealed a mean surgically induced astigmatism (SIA) of 1.17 D at 6 weeks and 1.04 D at 12 months. The side of the incision significantly affected SIA. At 6 weeks, temporal incisions yielded a mean SIA of 0.74 D and the nasal incisions, of 1.65 D. This trend in SIA persisted at 12 months: 0.71 D for temporal incisions and 1.41 D for nasal incisions. CONCLUSIONS: Cataract surgery using a horizontal clear corneal incision induced WTR astigmatism 6 weeks and 12 months postoperatively. Temporal incisions induced significantly less astigmatism than nasal incisions.

Aged↗
PubMed1997

Surgically induced astigmatism following a 4.0 mm sclerocorneal valve incision.

PURPOSE: To determine whether sutureless small incision cataract surgery reduces induced astigmatism over the long term. SETTING: University Eye Hospital, Vienna, Austria. METHODS: In a prospective study, we investigated surgically induced astigmatism in 63 cases of no-stitch, small incision cataract surgery with a 4.0 mm square sclerocorneal tunnel and implantation of a flexible intraocular lens. Follow-up was 4 to 5 years. Keratometry was measured with a Zeiss keratometer preoperatively and after 1 day, 1 week, 1, 3, and 9 months, and a median of 4.4 years. In 21 nonoperated eyes, we investigated the natural course of astigmatism over 5 years. RESULTS: The mean keratometric cylinder stabilized at 0.8 diopter (D) after 1 week and slightly decreased to 1.0 D after 4 to 5 years. Cravy's vector analysis showed an immediate against-the-rule (ATR) shift of -0.2 D that remained relatively stable until 9 months. Between 9 months and 4.4 years postoperatively, there was a statistically significant increase in ATR induced astigmatism from -0.2 to -0.5 D. The natural course of astigmatism in the nonoperated eyes showed an ATR shift of -0.1 D for the same period. CONCLUSION: The result show a small, though statistically significant amount of postoperatively induced astigmatism 4 to 5 years after no-stitch, small incision cataract surgery.

Aged↗
PubMed1997

Prospective, randomized vector analysis of astigmatism after three-, one-, and no-suture phacoemulsification.

PURPOSE: To compare surgically induced astigmatism and visual outcomes after three-, one-, and no-suture phacoemulsification. SETTING: Johns Hopkins Hospital, Baltimore, Maryland and Manhattan Eye, Ear, and Throat Hospital, New York, New York, USA. METHODS: This prospective, randomized study followed 131 patients treated with phacoemulsification with a 5.5 mm self-sealing scleral tunnel and implantation of a 5.5 mm poly(methyl methacrylate) posterior chamber lens. Radial 10-0 nylon sutures were used in the three- and one-suture groups. RESULTS: Mean astigmatism was greatest in the first postoperative week in all groups and stabilized after 8 weeks. The percentage of patients with with-the-rule (WTR) astigmatism increased from baseline in the one- and three-suture groups and decreased in the sutureless group. Mean uncorrected Snellen acuity was significantly better in the no- and one-suture groups than in the three-suture group at 1 week. There were no significant differences in uncorrected acuity at other times. No statistically significant differences in the surgically induced spherical equivalent were noted among the three groups during the 1 year follow-up. There was significantly less surgically induced keratometric astigmatism in the one-suture group at 4 (P = .03) and 8 (P = .007) weeks postoperatively. At all follow-ups, the sutureless group had the greatest proportion of patients, with significant ATR astigmatic shift (1 week, 17%; 4 weeks, 32%); and the lowest proportion of patients with significant WTR astigmatic shift (10% after 1 week). At 4 weeks, the percentage of patients with significant WTR shift in the one-suture group dropped to that in the sutureless group (10%); however, those in the one-suture group had less ATR astigmatic shift (16%). CONCLUSION: Sutureless and one-suture surgery resulted in a low percentage of WTR induced astigmatism 4 weeks postoperatively. Compared with sutureless surgery, the one-suture surgery resulted in less ATR shift.

Adult↗
PubMed1998

Relationship between preoperative axis of astigmatism and postoperative astigmatic change after superior scleral incision phacoemulsification.

PURPOSE: To evaluate the effect of the preoperative axis of astigmatism on the outcome of corneal astigmatism after sutured 5.2 to 5.7 mm superior incision phacoemulsification. SETTING: Departments of Opthalmology, Odense and Vejle Hospitals, Denmark. METHODS: Seventy-three consecutive patients with preoperative corneal astigmatism of 2.0 diopters (D) or less, axial length between 20.0 and 25.5 mm, and no eye disease except cataract were grouped according to preoperative with-the-rule (WTR) or against-the-rule (ATR) astigmatism. The keratometric cylinder, induced keratometric cylinder (subtraction), and induced cylinder (Jaffe) were measured and calculated 10 to 12 months postoperatively. RESULTS: The postoperative keratometric cylinder and induced keratometric cylinder were significantly higher in the ATR group (P < .00001; mean difference [95% confidence limits]: 0.76 D [0.54; 0.98] and 0.69 D [0.46; 0.92], respectively). There was no significant difference between groups in induced cylinder (Jaffe). CONCLUSION: The estimated differences were significantly in favor of patients with preoperative WTR astigmatism. The findings support using temporal incision in cases with a preoperative ATR axis of astigmatism.

Aged↗
PubMed1998

Two year follow-up of astigmatism after phacoemulsification with adjusted and unadjusted sutured versus sutureless 5.2 mm superior scleral incisions.

PURPOSE: To evaluate changes in astigmatism 6 months to 2 years after 5.2 mm superior scleral incision phacoemulsification using 3 closures. SETTING: Department of Ophthalmology, Vejle Hospital, Vejle, Denmark. METHODS: This long-term follow-up study included 75 consecutive phacoemulsification patients who were randomly allocated to 1 of 3 incision closures: 1 intraoperatively adjusted cross suture, 1 unadjusted cross suture, no suture. Postoperative astigmatism after 1 and 2 years was evaluated by keratometric cylinder, induced astigmatism (Naeser's polar values), induced cylinder (Jaffe's vector analysis), and vector decomposition (Olsen). The data were compared with 1 week values. RESULTS: In the previous study, median astigmatism after 6 months was similar in all 3 groups, but only the sutureless group showed early stability. Significant against-the-rule (ATR) changes were seen in the sutured cases (P < .01). The 1 and 2 year follow-up showed continued stability in the sutureless cases. The adjusted-suture group exhibited stability after 6 months, while the unadjusted-suture group showed a further tendency to change ATR. At 2 years, median ranges of astigmatism were -0.49 to -0.90 diopter (D) (Naeser), 0.77 to 1.02 D (Jaffe), and 96% to 98% ATR (Olsen). The intergroup differences were not statistically significant. CONCLUSION: Two year follow-up confirmed that sutureless closure led to early astigmatism stability. Using a suture prolonged the postoperative period of astigmatism instability, and if used without intraoperative adjustment, a tendency toward a less predictable outcome persisted after 2 years.

Aged↗
PubMed1997

Responses to DNA damage and regulation of cell cycle checkpoints by the ATM protein kinase family.

In mammalian cells, four protein kinases form the PI3-kinase-related protein kinase (PIK) superfamily. These four enzymes-FRAP, DNA-PK, ATM, and ATR-are distinguished by their large size (all are >2500 amino acids), their common primary sequence relatedness through the carboxy-terminal protein kinase domain, and their sequence similarity to the p110 lipid kinase subunit of PI3-kinase. FRAP (FKBP12 and rapamycin-binding protein kinase) participates in mitogenic and growth factor responses in G1 and may regulate specific mRNA translation signals. DNA-PK (DNA-dependent protein kinase), ATM (ataxia telangiectasia mutated), and ATR (ataxia telangiectasia and Rad 3 related) are thought to participate in responses to nuclear cues that activate DNA rearrangements or cell cycle arrests. Recent studies in this protein kinase family indicate an important role for ATM and ATR in a meiotic surveillance mechanism that may regulate proper chromosome transmission.

Adenosine Triphosphatases↗
PubMed1997

Atm-dependent interactions of a mammalian chk1 homolog with meiotic chromosomes.

BACKGROUND: Checkpoint pathways prevent cell-cycle progression in the event of DNA lesions. Checkpoints are well defined in mitosis, where lesions can be the result of extrinsic damage, and they are critical in meiosis, where DNA breaks are a programmed step in meiotic recombination. In mitotic yeast cells, the Chk1 protein couples DNA repair to the cell-cycle machinery. The Atm and Atr proteins are mitotic cell-cycle proteins that also associate with chromatin during meiotic prophase I. The genetic and regulatory interaction between Atm and mammalian Chk1 appears to be important for integrating DNA-damage repair with cell-cycle arrest. RESULTS: We have identified structural homologs of yeast Chk1 in human and mouse. Chk1(Hu/Mo) has protein kinase activity and is expressed in the testis. Chk1 accumulates in late zygotene and pachytene spermatocytes and is present along synapsed meiotic chromosomes. Chk1 localizes along the unsynapsed axes of X and Y chromosomes in pachytene spermatocytes. The association of Chk1 with meiotic chromosomes and levels of Chk1 protein depend upon a functional Atm gene product, but Chk1 is not dependent upon p53 for meiosis I functions. Mapping of CHK1 to human chromosomes indicates that the gene is located at 11q22-23, a region marked by frequent deletions and loss of heterozygosity in human tumors. CONCLUSIONS: The Atm-dependent presence of Chk1 in mouse cells and along meiotic chromosomes, and the late pachynema co-localization of Atr and Chk1 on the unsynapsed axes of the paired X and Y chromosomes, suggest that Chk1 acts as an integrator for Atm and Atr signals and may be involved in monitoring the processing of meiotic recombination. Furthermore, mapping of the CHK1 gene to a region of frequent loss of heterozygosity in human tumors at 11q22-23 indicates that the CHK1 gene is a candidate tumor suppressor gene.

Amino Acid Sequence↗
PubMed2002

A simplified broadband coupling approach applied to chemically robust sol-gel, planar integrated optical waveguides.

A new generation waveguide spectrometer with broadband coupling capabilities has been developed. As opposed to previous devices, this attenuated total reflection (ATR) spectrometer is much simpler in design, is more chemically robust, and transmits light down to at least 400 nm. The attenuated total reflection element consists of a single-mode, planar integrated optical waveguide fabricated by dip-coating a approximately 300 nm thick, sol-gel composite layer on a glass substrate. A commercially available prism is used as the incoupler with an integral holographic diffraction grating acting as the dispersive outcoupling element. The transmission of narrow band-pass filters was used to compare the response of the waveguide spectrometer to that of a conventional transmission instrument. Spectral resolution was assessed by measuring the fwhm of various laser lines, which were found to range from 0.5 to 1.3 nm. The measured limits of detection for the waveguide spectrometer from 400 to 600 nm are 8.0 and 10.1 milliabsorbance units for TE and TM polarizations, respectively. Finally, to demonstrate the application of this technology to a molecular film confined to a solid-liquid interface, visible ATR spectra of an adsorbed submonolayer of horse heart cytochrome c were acquired. A procedure to correct the waveguide spectra for the wavelength dependence in ATR path length is described.

Animals↗
PubMed2002

Single-pass attenuated total reflection Fourier transform infrared spectroscopy for the prediction of protein secondary structure.

Principal component regression (PCR) was applied to a spectral library of proteins in H2O solution acquired by single-pass attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy. PCR was used to predict the secondary structure content, principally alpha-helical and the beta-sheet content, of proteins within a spectral library. Quantitation of protein secondary structure content was performed as a proof of principle that use of single-pass ATR-FT-IR is an appropriate method for protein secondary structure analysis. The ATR-FT-IR method permits acquisition of the entire spectral range from 700 to 3900 cm(-1) without significant interference from water bands. An "inside model space" bootstrap and a genetic algorithm (GA) were used to improve prediction results. Specifically, the bootstrap was utilized to increase the number of replicates for adequate training and validation of the PCR model. The GA was used to optimize PCR parameters, particularly wavenumber selection. The use of the bootstrap allowed for adequate representation of variability in the amide A, amide B, and C-H stretching regions due to differing levels of sample hydration. Implementation of the bootstrap improved the robustness of the PCR models significantly; however, the use of a GA only slightly improved prediction results. Two spectral libraries are presented where one was better suited for beta-sheet content prediction and the other for alpha-helix content prediction. The GA-optimized PCR method for alpha-helix content prediction utilized 120 wavenumbers within the amide I, II, A, B, and IV and the C-H stretching regions and 18 factors. For beta-sheet content predictions, 580 wavenumbers within the amide I, II, A, and B and the C-H stretching regions and 18 factors were used. The validation results using these two methods yielded an average absolute error of 1.7% for alpha-helix content prediction and an average absolute error of 2.3% for beta-sheet content prediction. After the PCR models were developed and validated, they were used to predict the alpha-helix and beta-sheet content of two unknowns, casein and immunoglobulin G.

Multivariate Analysis↗