Water Absorption Peak Research Articles

Near-infrared laser thermal conjunctivoplasty

Conjunctivochalasis is a common cause of tear dysfunction due to the conjunctiva becoming loose and wrinkly with age. The current solutions to this disease include either surgical excision in the operating room, or thermoreduction of the loose tissue with hot wire in the clinic. We developed a near-infrared laser thermal conjunctivoplasty system. The system utilizes a 1460-nm programmable laser diode system as the light source. At this wavelength, a water absorption peak exists and the blood absorption is minimal, so the heating of redundant conjunctiva is even and there is no bleeding. A miniaturized handheld probe delivers the laser light and reshapes the laser into a 10 × 1 mm2 line on the working plane. A foot pedal is used to deliver a preset number of calibrated laser pulses. A fold of loose conjunctiva is grasped by a pair of forceps. The NIR laser light is delivered through an optical fiber and a laser line is aimed exactly on the conjunctival fold by a cylindrical lens. Ex vivo experiments using porcine eye was performed to investigate the induced shrinkage of conjunctiva and decide the optimal laser parameters. It was found that up to 45% of conjunctiva shrinkage could be achieved.

Exploring Functionality of Hard and Soft Wheat Flour Blends for Improved End‐Use Quality Prediction

Blending wheat or flour to meet end‐use requirements is a critical part of the production process to deliver consistent quality products. The functionality of commercial Canadian hard red wheat flour (HWF) and soft red wheat flour (SWF) blends with ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 (HWF/SWF, w/w) was investigated with new and standard methods to discern which functional properties may be indicators of bread quality and processing performance. Rheological characteristics including farinograph water absorption behavior, dough development time (DT), stability, extensigraph extensibility, and gluten aggregation of wheat flours were significantly influenced by the proportion of HWF in blends of SWF and HWF (P < 0.05). The SWF content in the blends had negative linear relationships with the protein content, lactic acid solvent retention capacity, water absorption, and GlutoPeak peak torque. Polynomial relationships were observed for sodium dodecyl sulfate sedimentation volume, DT, stability, extensibility, resistance, GlutoPeak peak time, and bread loaf volume with the amount of SWF in blends. The results indicate that linear responses may be more closely tied to protein content, whereas polynomial responses may be more indicative of protein quality and baking performance. The GlutoPeak peak time was sensitive to the addition of HWF in the blends, showing a significant change in gluten aggregation kinetics between the 0 and 25% HWF samples. Principal component analysis (PCA) confirmed that GlutoPeak peak time was a significant factor in differentiating the 0% HWF. Protein secondary structures identified in the final baked bread were also PCA factors differentiating the 0% HWF sample. Although the 0% bread sample did not deviate from the observed polynomial trend for bread loaf volume, the differences in bread protein secondary structures may translate into differences in processing tolerance in commercial settings.

Effects of ozone treatment on physicochemical properties of Korean wheat flour.

The objective of this study was to investigate the effects of ozone treatment on the physicochemical properties of Korean wheat flour. Wheat flour samples were treated with ozone gas at 120 ppm for 15, 30, 45, and 60 min. Color b value, pH, and mold of flour decreased as exposure time to ozone increased. The water absorption index, peak viscosity, and final viscosity of flour increased by ozone treatment. Photomicrographs of flour suspensions under polarized light showed granules tended to lose birefringence owing to ozone during swelling. The result of SDS-PAGE showed that the intensity of protein bands at low molecular weights slightly increased in ozone-treated flours compared to the intensity in the control flour. The results of this study showed ozone gas affected the starch and protein of wheat flour, suggesting a need for further investigation on structural changes in starch and protein by ozone.

Principal component analysis and correlation studies of spring wheats in relation to cookie making quality

ABSTRACTQuality of cookies is profoundly influenced by the physicochemical and rheological properties of wheat grains. Therefore, it is pivotal to explore right choice of wheat cultivar. Current study was designed to gauge the relationship between wheat grain physiognomies and flour rheological behaviour with cookie characteristics. The outcomes depicted that selected wheat varieties varied significantly (p < 0.01) in various parameters like thousand kernel weight, test weight, pearling value, Pelshenke and zeleny value. In correlation, particle size index correlated negatively (r = −0.67) with protein content and positively with water absorption. Spread factor of cookies was influenced by particle size index (r = −0.63), Pelshenke (r = −0.62), water absorption (r = −0.60), and mixographic peak height (r = 0.85). Principal component analysis illustrated that thousand kernel weight, grain length, and width were major components in determining the water absorption of wheat flour. However, spread factor of cookies was partly depicted from Pelshenke value and partly from particle size index.

The origin of the Debye relaxation in liquid water and fitting the high frequency excess response.

We critically review the literature on the Debye absorption peak of liquid water and the excess response found on the high frequency side of the Debye peak. We find a lack of agreement on the microscopic phenomena underlying both of these features. To better understand the molecular origin of Debye peak we ran large scale molecular dynamics simulations and performed several different distance-dependent decompositions of the low frequency dielectric spectra, finding that it involves processes that take place on scales of 1.5-2.0 nm. We also calculated the k-dependence of the Debye relaxation, finding it to be highly dispersive. These findings are inconsistent with models that relate Debye relaxation to local processes such as the rotation/translation of molecules after H-bond breaking. We introduce the spectrumfitter Python package for fitting dielectric spectra and analyze different ways of fitting the high frequency excess, such as including one or two additional Debye peaks. We propose using the generalized Lydanne-Sachs-Teller (gLST) equation as a way of testing the physicality of model dielectric functions. Our attempts at fitting the experimental spectrum using the gLST relation as a constraint indicate that the traditional way of fitting the excess response with secondary and tertiary Debye relaxations is problematic. All of our work is consistent with the recent theory of Popov et al. (2016) that Debye relaxation is due to the migration of Bjerrum-like defects in the hydrogen bond network. Under this theory, the mechanism of Debye relaxation in liquid water is similar to the mechanism in ice, but the heterogeneity and power-law dynamics of the H-bond network in water results in excess response on the high frequency side of the peak.

Induction and analysis for NIR features of frequently-used mineral traditional Chinese medicines

In order to provide theoretical basis for the rapid identification of mineral traditional Chinese medicines(TCM) with near infrared (NIR)diffuse reflectance spectroscopy, Characteristic NIR spectra of 51 kinds of mineral TCMs were generalized and compared on the basis of the previous research, and the characteristic spectral bands were determined and analyzed by referring to mineralogical and geological literatures. It turned out that the NIR features of mineral TCMs were mainly at 8 000-4 000 cm ⁻¹ wavebands, which can be assigned as the absorption of water, -OH and[CO3 ²⁻] and so on. Absorption peaks of water has regularity as follows, the structure water and -OH had a combined peak which was strong and keen-edged around 7 000 cm ⁻¹, the crystal water had two strong peak around 7 000 cm ⁻¹ and 5 100 cm ⁻¹, and water only has a broad peak around 5 100 cm ⁻¹. Due to the differences in the crystal form and the contents of water in mineral TCMs, NIR features of water in mineral TCMs which could be used for identification were different. Mineral TCMs containing sulfate are rich in crystal water, mineral TCMs containing silicate generally had structure water, and mineral TCMs containing carbonate merely had a little of water, so it was reasonable for the use of NIR spectroscopy to classify mineral TCMs with anionic type. In addition, because of the differences in cationic type, impurities, crystal form and crystallinity, mineral TCMs have exclusive NIR features at 4 600-4 000 cm ⁻¹, which can be assigned as Al-OH, Mg-OH, Fe-OH, Si-OH,[CO3 ²⁻] and so on. Calcined mineral TCMs are often associated with water and main composition changes, also changes of the NIR features, which could be used for the monitoring of the processing, and to provide references for the quality control of mineral TCMs. The adaptability and limitation of NIR analysis for mineral TCMs were also discussed:the majority of mineral TCMs had noteworthy NIR features which could be used for the NIR analysis. And the NIR features of a few mineral TCMs were inapparent, such as Fluoritum, Realgar and Cinnabar, for which the Raman spectroscopy can be adopted alternatively.

Three-Dimensional Measurement of Ice Crystals in Frozen Materials by Near-Infrared Imaging Spectroscopy

A novel technique was developed to recognize ice crystals in biological materials and to analyze their three-dimensional morphology using a Cryogenic Micro-Slicer Spectral Imaging System with a micro-slicer unit and a near-infrared spectral imaging unit. Consecutive cross-sections of a frozen sample were exposed by the multi-slicing operations with a minimum thickness of 1 µm, and their images were taken by the imaging unit. Spectroscopic analysis using a near-infrared spectrum meter showed an absorption peak at 1460 nm for pure water. Based on the observations of the absorption band of ice crystals in the wavelength range of 1450–1570 nm and its peak at 1495 nm, a commodity-type bandpass filter with a central wavelength of 1500 nm was adopted to identify ice crystals in near-infrared images. The absorption peak of water exhibited a tendency to move toward longer wavelengths with decreasing sample temperature from 25 °C to −15 °C. The filtered images of ice crystals in frozen samples were darker than the other components at the peak wavelength of ice crystals. The three-dimensional reconstructed morphology of ice crystals revealed that they were formed along the direction of heat transfer while freezing. The proposed method provides a novel tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand.

Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength () and surface moisture () over the optical domain of 350–2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content 24% ( 0.97), but underestimated reflectance for between 24–30% ( 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well ( 0.99) but is limited to 4% 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner ( = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach.

Deep optical imaging of tissue using the second and third near-infrared spectral windows.

Light at wavelengths in the near-infrared (NIR) region allows for deep penetration and minimal absorption through high scattering tissue media. NIR light has been conventionally used through the first NIR optical tissue window with wavelengths from 650 to 950 nm. Longer NIR wavelengths had been overlooked due to major water absorption peaks and a lack of NIR-CCD detectors. The second NIR spectral window from 1100 to 1350 nm and a new spectral window from 1600 to 1870 nm, known as the third NIR optical window, were investigated. Optical attenuation measurements from thin tissue slices of normal and malignant breast and prostate tissues, pig brain, and chicken tissue were obtained in the spectral range from 400 to 2500 nm. Optical images of chicken tissue overlying three black wires were also obtained using the second and third spectral windows. Due to a reduction in scattering and minimal absorption, longer attenuation lengths and clearer optical images could be seen in the second and third NIR optical windows compared to the conventional first NIR optical window. A possible fourth optical window centered at 2200 nm was noted.

Effect of ingredients on rheological, nutritional and quality characteristics of fibre and protein enriched baked energy bars

Effect of substitution of brown flour (BF) with fiber rich ingredient mixture, FRIM (banana flour, psyllium husk, partially defatted coconut flour and oats) and protein rich ingredient mixture, PRIM (chickpea flour, sesame, soya protein isolate and whey protein concentrate) at the levels of 25, 50 and 75% on the rheological, nutritional and quality characteristics of baked energy bars (BEB) were studied. Use of increasing amount of FRIM increased farinograph water absorption and amylograph peak viscosity while PRIM decreased the aforementioned parameters. Addition of FRIM or PRIM increased the bar dough hardness and decreased cohesiveness and springiness. The overall quality score of BEB increased only up to the substitution of 50% of BF with FRIM or PRIM. The BEB with 50% FRIM and PRIM remained chemically stable during storage up to 3months and showed 9 times increase in dietary fiber content and about 2 times increase in protein content respectively.

High-energy pulsed Raman fiber laser for biological tissue coagulation

We demonstrate a high-energy pulsed Raman fiber laser (RFL) with an emission wavelength of 1.44 μm, corresponding to an absorption peak of water. Microsecond pulses with >20 mJ/pulse and >40 W peak power were generated, well above the threshold for tissue coagulation and ablation. Here, we focus on the optical characterization and optimization of high-energy and high-power RFLs excited by an ytterbium fiber laser, comparing three configurations that use different Raman gain fibers, but all of which were prepared with a one-side opened, free-run mode without output mirrors. We show that the free-run configuration can generate sufficiently high energy without requiring a closed cavity design. Experimental RFL characteristics corresponded well with numerical simulations. We discuss the Stokes beam generation process in our system and loss mechanisms mainly associated with fiber Bragg gratings.

Contraction-Induced Changes in Hydrogen Bonding of Muscle Hydration Water.

Protein–water interaction plays a crucial role in protein dynamics and hence function. To study the chemical environment of water and proteins with high spatial resolution, synchrotron radiation-Fourier transform infrared (SR-FTIR) spectromicroscopy was used to probe skeletal muscle myofibrils. Observing the OH stretch band showed that water inside of relaxed myofibrils is extensively hydrogen-bonded with little or no free OH. In higher-resolution measurements obtained with single isolated myofibrils, the water absorption peaks were relatively higher within the center region of the sarcomere compared to those in the I-band region, implying higher hydration capacity of thick filaments compared to the thin filaments. When specimens were activated, changes in the OH stretch band showed significant dehydrogen bonding of muscle water; this was indicated by increased absorption at ∼3480 cm–1 compared to relaxed myofibrils. These contraction-induced changes in water were accompanied by splitting of the amide I (C=O) peak, implying that muscle proteins transition from α-helix to β-sheet-rich structures. Hence, muscle contraction can be characterized by a loss of order in the muscle–protein complex, accompanied by a destructuring of hydration water. The findings shed fresh light on the molecular mechanism of muscle contraction and motor protein dynamics.

Influence of Freeze-Dried Shrimp Meat in Pasta Processing Qualities of Indian T. durum Wheat

The present study aims to understand the influence of freeze-dried shrimp (Penaeus monodon) meat (SM) at different levels (2.5, 5, and 10%; w/w) in pasta processing. The rheological characteristics studies of SM-wheat flour blends indicated that dough stability increased with the increased addition of SM in the blends, whereas farinograph water absorption and amylograph peak viscosity decreased. Cooking loss increased with increasing levels of SM in the pasta (7.3% in 10% SM pasta; 6.7% in control pasta). However, all pasta samples were in the acceptable range. Color analysis of the pasta sample indicated that the L values increased with increasing levels of pasta. The instrumental texture of cooked pasta indicated that 10% SM pasta was significantly (p < 0.05) firmer (1.84 N) than that of the control (1.35 N). Microstructure studies revealed that incorporation of SM in the pasta had a better protein network. Pasta with 5% SM had the highest mean score for all sensory attributes, with increased levels of essential nutrients, fatty acids such as eicosapentaenoic acid and docosahexaenoic acid, and amino acids such as lysine.

Genetic analysis of the Fourier-transform infrared spectra of bovine milk with emphasis on individual wavelengths related to specific chemical bonds

Fourier-transform infrared (FTIR) spectra are used to predict the fat, protein, casein, and lactose contents of milk. These estimates are currently used to predict the individual estimated breeding values of animals. The objective of the present study was to estimate the genetic variation and heritabilities of the milk transmittance spectrum at each individual FTIR wave. Milk was sampled once per cow from a total of 1,064 Italian Brown Swiss cows from 30 herds, sired by 50 artificial insemination sires. The FTIR spectra of all samples were collected within 3h of sampling from 25mL of milk. The obtained spectral range comprised wavenumbers 5,000 to 930×cm−1, corresponding to wavelengths 2.00 to 10.76μm and frequencies from 149.9 to 27.9THz, for a total of 1,056 waves. These were acquired using a MilkoScan FT120 FTIR interferometer (Foss Electric A/S, Hillerød, Denmark). Each spectral data point was treated as a single trait and analyzed using an animal model REML method. The results indicated that the transmittance of the bovine milk FTIR spectrum was heritable for most individual waves in the wavenumber interval from 5,000 to 930×cm−1. Moreover, the transmittance of contiguous FTIR waves was much more highly correlated in terms of the average value and phenotypic variation, compared with genetic variation. In the present study, we characterized 5 regions of the FTIR spectrum that were relevant to the analysis of milk; 2 regions, one in the transition area between the short-wavelength infrared (SWIR) and mid-wavelength infrared (MWIR) divisions of the electromagnetic spectrum (SWIR-MWIR region) and another very short region in the MWIR division (MWIR-2 region), were characterized by very high phenotypic variability in the transmittance of individual milk samples within each wave. This was caused by the absorption peaks of water, which can mask the effects of other important milk components. These regions also showed high genetic variability in transmittance, and the heritability estimates of individual waves were generally very low (with some exceptions). The 3 other identified regions contained many transmittance peaks that represented important chemical bonds; these showed much lower phenotypic and genetic variability in terms of individual waves, but relatively higher and less variable heritability estimates. Among them, the SWIR region (near-infrared) showed a peculiar cyclic pattern of the heritability coefficients of transmittance, the MWIR-1 region was particularly important for the estimation of fat, and the MWIR-LWIR region (also known also as the “fingerprint region”) had 3 areas of relatively high heritability. In summary, we found that the transmittance data from the FTIR spectra of milk have genetic variability that may prove useful for the direct genetic improvement of dairy species, rather than only through indirect phenotypic predictions of individual milk quality and technological traits.

Effect of steeping additives on tef starch extraction and its quality

AbstractTef is an indigenous African cereal and considered as lost crop of Africa. There is no research on the effect of steeping additives on the quality of isolated tef starch. A white tef grain was milled and steeped in distilled water, sodium hydroxide, lactic acid, metabisulfite, and a combination of lactic acid and metabisulfite. A combination of metabisulfite and lactic acid improves the starch yield, but steeping with sodium hydroxide produces the highest starch purity (lowest protein content). Both the Rapid Visco Analyzer and a Rheometer showed similar pasting properties of starches independent of the treatment. The different steeping additives showed differences in pasting properties. Sodium hydroxide showed the highest peak, breakdown and set back viscosity compared to the other steeping additives. Extracted tef starches using sodium hydroxide as steeping additives also showed higher gelatinization temperatures. According to principle component analysis (PCA), the different properties of tef starch extracted with sodium hydroxide steeping is apparently due to its lower protein content. SEM and CLSM indicated that sodium hydroxide is a very effective solvent to solubilize the protein matrix surrounding the compound starch granule to produce more single starch granule during extraction. The low protein content probably result in faster water absorption and higher peak viscosity and lower pasting temperature. Different steeping additives can affect the functionality of tef starches and this need to be considered when comparing properties of starches extracted with different additives.

3 μm CW lasers for myringotomy and microsurgery.

This paper describes the development and implementation of 3 μm lasers for myringotomy and microsurgery. Two different lasers were investigated. The first, an Er-doped, CW zirconate glass fiber laser optically pumped by a 970 nm diode laser, emitted > 1 W of CW power at 2.76 μm with concomitant green incoherent emission that served as a convenient visible illumination beam. The second, a 1 W CW Er:YAG solid-state laser also optically pumped by a 970 nm diode laser, emitted > 1 W of CW power at 2.94 μm, coincident with the strongest infrared water absorption peak. Running CW, both lasers are expected to avoid the loud acoustical shocks associated with pulsed lasers. Myringotomies were carried out with the Er:YAG laser on anaesthetized guinea pigs and the effects of the laser were documented. Laser ablated samples of tympanic membrane, soft tissue and bone were histologically examined. Histology results indicated that the CW Er:YAG laser is a potential candidate for a new myringotomy tool and possibly for otologic microsurgery, but deliverable power levels need to be increased to the 2 W (or higher) level. This work was funded under NIH SBIR Grant No. 5R44DC004899.

Evaluation of Quality Characteristics of High Nutrient Dense Complementary Food from Mixtures of Malted Quality Protein Maize (Zea mays L.) and Steamed Cowpea (Vigna unguiculata)

Quality Protein Maize is an improved variety of maize which contains higher amount of lysine and tryptophan. Cowpea is an indigenous legume widely consumed in Nigeria. Quality Protein Maize was malted by steeping, germinating, drying and milling while cowpea was dehulled, steamed, dried and milled. The resulting flours were blended to produce complementary food at ratios of 100:0; 70:30 (Quality Protein Maize and Cowpea). The quality characteristics of the blends were assessed by determining the chemical composition, sensory properties, functional and pasting characteristics. The results showed that 30% substitution of cowpea and malting increased the protein level significantly (p>0.05). Potassium, Magnesium and Phosphorus also increased with supplementation. The water absorption capacity, bulk density, peak and final viscosities were significantly (p>0.05) reduced in the malted samples. All the formulated diets were acceptable to the nursing mothers who served as the panelists. The low bulk, water absorption capacity and viscosity of the germinated samples encouraged addition of more solid to the thin gruel produced from it; such addition increased the energy and other nutrients of the gruel as required by infants for growth and development.

Removal of Sea Salt Hydrate Water from Seawater-Derived Samples by Dehydration

Aerosol particles produced from bubble bursting of natural seawater contain both sea salts and organic components. Depending on the temperature, pressure, and speed of drying, the salt components can form hydrates that bind water, slowing evaporation of the water, particularly if large particles or thick layers of salts undergo drying that is nonuniform and incomplete. The water bound in these salt hydrates interferes with measuring organic hydroxyl and amine functional groups by Fourier transform infrared (FTIR) spectroscopy because it absorbs at the same infrared wavelengths. Here, a method for separating the hydrate water in sea salt hydrates using freezing and then heating in warm, dry air (70 °C) is evaluated and compared to other methods, including spectral subtraction. Laboratory-generated sea salt analogs show an efficient removal of 89% of the hydrate water absorption peak height by 24 h of heating at atmospheric pressure. The heating method was also applied to bubbled submicrometer (Sea Sweep), generated bulk (Bubbler), and atomized seawater samples, with efficient removal of 5, 22, and 39 μg of hydrate water from samples of initial masses of 11, 30, 58 μg, respectively. The strong spectral similarity between the difference of the initial and dehydrated spectra and the laboratory-generated sea salt hydrate spectrum provided verification of the removal of hydrate water. In contrast, samples of submicrometer atmospheric particles from marine air masses did not have detectable signatures of sea salt hydrate absorbance, likely because their smaller particles and lower filter loadings provided higher surface area to volume ratios and allowed faster and more complete drying.

Using near infrared measurement of water content as a cue for detecting biological materials

This paper uses the spectral characteristics of water as a cue to detect biological materials in a scene. The spectra of a wide variety of materials were measured; most of the biological materials showed a spectral feature corresponding to the absorption peak of water at 962 nm. A machine vision system that used two narrowband near infrared light sources and a conventional CCD camera is described. The ability of the system to detect biological material is demonstrated in a series of examples. Water content is not an infallible indicator that a material is biological-wet inanimate surfaces will give a false positive, and some tissues are surrounded by highly scattering, impermeable layers that conceal internal water. Nonetheless, in this paper, we will show that many tissues do give a strong response to this feature and dry, nonbiological materials do not.

Structural Water Cluster As a Possible Proton Acceptor in the Adduct Decay Reaction of Oat Phototropin 1 LOV2 Domain

LOV domains (Light, Oxygen, Voltage) are the light-sensory modules of phototropins, the blue-light photoreceptor kinases in plants, and of a wide variety of flavoproteins found in all three domains of life. These 12 kDa modules bind a flavin chromophore (FMN or FAD) noncovalently and undergo a photochemical activation in which the sulfur atom of a conserved cysteine forms an adduct to the C(4a) carbon of the flavin. The adduct breaks spontaneously in a base-catalyzed reaction involving a rate-limiting proton-transfer step, regenerating the dark state in seconds. This photocycle involves chromophore and protein structural changes that activate the C-terminal serine/threonine kinase. Previous studies (Biochemistry 2007, 46, 7016-7021) showed that decreased hydration obtained at high glycerol concentrations stabilizes the adduct state in a manner similar to that attained at low temperatures, resulting in much longer adduct decay times. This kinetic effect was attributed to an increased protein rigidity that hindered structural fluctuations necessary for the decay reaction. In this work, we studied the adduct decay kinetics of oat phototropin 1 (phot1) LOV2 at varying hydration using a specially designed chamber that allowed for measurement of UV-visible and FTIR spectra of the same samples. Therefore, we obtained LOV protein concentrations, adduct decay kinetics, and the different populations of bound water by deconvolution of the broad water absorption peak around 3500 cm(-1). A linear dependence of the adduct decay rate constant on the concentration of double and triple hydrogen-bonded waters strongly suggests that the adduct decay is a pseudo-first-order reaction in which both the adduct and the strongly bound waters are reactants. We suggest that a cluster of strongly bound water functions as the proton acceptor in the rate-limiting step of adduct decay.