Effect of autoclave postpolymerization treatments on the fracture toughness of autopolymerizing dental acrylic resins

Introduction: Microwave and water bath postpolymerization have been suggested as methods to improve the mechanical properties of heat and autopolymerizing acrylic resins. However, the effects of autoclave heating on the fracture properties of autopolymerizing acrylic resins have not been investigated. Purpose: The aim of this study was to assess the effectiveness of various autoclave postpolymerization methods on the fracture properties of 3 different autopolymerizing acrylic resins. Methods: Forty-two specimens of 3 different autopolymerizing acrylic resins (Orthocryl, Paladent RR and Futurajet) were fabricated (40x8x4mm), and each group was further divided into 6 subgroups (n=7). Control group specimens remained as processed (Group 1). The first test group was postpolymerized in a cassette autoclave at 135°C for 6 minutes and the other groups were postpolymerized in a conventional autoclave at 130°C using different time settings (5, 10, 20 or 30 minutes). Fracture toughness was then measured with a three-point bending test. Data were analyzed by ANOVA followed by the Duncan test (α=0.05). Results: The fracture toughness of Orthocryl and Paladent-RR acrylic resins significantly increased following conventional autoclave postpolymerization at 130°C for 10 minutes (P<.05). However, the fracture toughness of autoclave postpolymerized Futurajet was not significantly different than its control specimens (P<.05). The fracture toughness of Futurajet was significantly less than Paladent RR and Orthocryl specimens when autoclaved at 130°C for 10 minutes. Conclusions: Within the limitations of this study, it can be suggested that autoclave postpolymerization is an effective method for increasing the fracture toughness of tested autoploymerized acrylic resins.     

Dilute phosphoric acid-catalysed hydrolysis of municipal bio-waste wood shavings using autoclave parr reactor system

The visibility of using municipal bio-waste, wood shavings, as a potential feedstock for ethanol production was investigated. Dilute acid hydrolysis of wood shavings with H?PO? was undertaken in autoclave parr reactor. A combined severity factor (CSF) was used to integrate the effects of hydrolysis times, temperature and acid concentration into a single variable. Xylose concentration reached a maximum value of 17 g/100 g dry mass corresponding to a yield of 100% at the best identified conditions of 2.5 wt.% H?PO?, 175 °C and 10 min reaction time corresponding to a CSF of 1.9. However, for glucose, an average yield of 30% was obtained at 5 wt.% H?PO?, 200 °C and 10 min. Xylose production increased with increasing temperature and acid concentration, but its transformation to the degradation product furfural was also catalysed by those factors. The maximum furfural formed was 3 g/100 g dry mass, corresponding to the 24% yield.     

Kinetic modelling of steam gasification of various woody biomass chars: influence of inorganic elements

A study was performed on the influence of wood variability on char steam gasification kinetics. Isothermal experiments were carried out in a thermobalance in chemical regime on various wood chars produced under the same conditions. The samples exhibited large differences of average reaction rate. These differences were linked neither with the biomass species nor age and may be related to the biomass inorganic elements. A modelling approach was developed to give a quantitative insight to these observations. The grain model was used on one biomass of reference for temperatures between 750 and 900 °C and steam partial pressures between 0 and 0.27 bar. The model was applied to the other samples through the addition of an integral parameter specific to each sample. A satisfactory correlation was found between this parameter and the ratio potassium/silicium. This result highlighted the catalytic effect of potassium and inhibitor effect of silicium on the reaction.     

Effect of complete extraction and re-addition of manganese on thermoluminescence of pea Photosystem II preparations

Thermoluminescence of Photosystem II particles isolated from pea chloroplasts using digitonin and Triton X-100 was measured after 1 min illumination at a certain temperature (T(ex)) followed by illumination during cooling (40 Cdeg/min) to a lower temperature. Glow curves of the particles are characteristic of the photosynthetic oxygen-evolving material studied earlier. Complete (more than 95%) removal of Mn from the Photosystem II particles abolishes thermoluminescence bands around 0° C, related to the oxygen-evolving system, but the thermoluminescence bands peaking around -30°C (TL(-30)), -55°C (TL_ (-55)) and between-68 and -85° C, depending on Tex(TLv), remain unaltered. The bands are characterized by different dependence on T,x. The TL(-30), TL(-55) and TL v bands can also be observed in the glow curve of isolated pea and spinach chloroplasts. Re-addition of MnCI (2) (2 μM, corresponding to nearly 4 Mn atoms per reaction center of Photosystem II) to the Mn-depleted particles does not reactivate the thermoluminescence bands around 0° C. However, it does lead to suppression of TL(-30) accompanied by parallel activation of TL(-55), revealing competition of the TL (-30) and TL(-55) for charges generated by the reaction center. These data, as well as the results on the effect of inhibitors and electron donors to Photosystem II, show that positive charges contributing to the TL(-30), TL (-55) and TL v thermoluminescence bands are located on secondary electron donors of Photosystem II which do not require Mn and are located closer to the reaction center than the Mn-containing, water-oxidizing enzyme.     

Comparison of body cooling methods on physiological and perceptual measures of mildly hyperthermic athletes

Hyperthermia is common among athletes and in a variety of environments. The purpose of this study was to evaluate the effectiveness of cooling methods on core body temperature, heart rate (HR), and perceptual readings in individuals after exercise. Sixteen subjects (age: 24 ± 6 years, height: 182 ± 7 cm, weight: 74.03 ± 9.17 kg, and body fat: 17.08 ± 6.23%) completed 10 exercise sessions in warm conditions (WBGT: 26.64 ± 4.71°C) followed by body cooling by 10 different methods. Cooling methods included cold water immersion (CWI), shade, Port-a-Cool? (FAN), Emergency Cold Containment System? (ECCS), Rehab. Hood? (HOOD), Game Ready Active Cooling Vest? (GRV), Nike Ice Vest? (NIV), ice buckets (IBs), and ice towels (IT). These cooling modes were compared with a control (SUN). Rectal temperature (T(re)), HR, thermal sensation, thirst sensation, and a 56-question Environmental Symptoms Questionnaire (ESQ) were used to assess physiological and perceptual data. Average T(re) after exercise across all trials was 38.73 ± 0.12°C. After 10 minutes of cooling, CWI (-0.65 ± 0.29°C), ECCS (-0.68 ± 0.24°C), and IB (-0.74 ± 0.34°C) had significantly (p < 0.006) greater decreases in T(re) compared with that in SUN (-0.42 ± 0.15°C). The HR after 10 minutes of cooling was significantly (p < 0.006) lower for CWI (82 ± 15 b·min(-1)), ECCS (87 ± 14 b·min(-1)), and IT (84 ± 15 b·min(-1)) when compared with SUN (101 ± 15 b·min(-1)). The thermal sensation between modalities was all significantly (p < 0.006) lower (CWI: 1.5 ± 0.5; Fan: 3.0 ± 1.0; ECCS: 4.5 ± 1.0; Hood: 4.5 ± 0.5; GRV: 4.0 ± 0.5; NIV: 4.5 ± 1.0; IB: 4.0 ± 1.0; IT: 3.0 ± 1.0) when compared with SUN (5.5 ± 0.5), except for Shade (5.0 ± 1.0). There were no significant differences (p > 0.006) in thirst sensation between modalities. The ESQ scores were significantly (p < 0.006) lower for CWI (1 ± 6), Fan (4 ± 5), and IT (3 ± 8) compared with that for SUN (13 ± 12). In conclusion, when athletes experience mild hyperthermia, CWI, ECCS, and IB resulted in a significantly greater decrease in T(re). These cooling strategies are recommended to decrease T(re) during a brief recovery period between exercise bouts.     

Optimization of production and reaction conditions of polygalacturonase from Byssochlamys fulva

In the present study, the optimization of production and reaction conditions of polygalacturonase produced by a fungus Byssochlamys fulva MTCC 505 was achieved. The production of polygalacturonase with a considerable activity of 1.28 IU/ml was found when the culture was shaken at 30°C for 5 days in 100 ml of medium containing (w/v) 10 g/l pectin, 2 g/l NaNO?, 1 g/l KH?PO?, 0.5 g/l KCl, 0.5 g/l MgSO?. 7H?O, 0.001 g/l FeSO?. 7H?O, 0.001 g/l CaCl?. The best carbon and nitrogen source for this enzyme were pectin (1%) and Ca(NO?)? (0.1%), respectively. The enzyme gave maximum activity at incubation time of 72 h, temperature of 30°C and pH 4.5. During the optimization of reaction conditions, the enzyme showed maximum activity in sodium citrate buffer (50 mM) of pH 5.5 at 50°C reaction temperature for 15 minutes of incubation. The enzyme showed greater affinity for polygalacturonic acid as substrate (0.5%). Km and Vmax values were 0.15 mg/ml and 4.58 μmol/ml/min. The effect of various phenolics, thiols, protein inhibitors and metal ions on the enzyme activity was investigated. The enzyme was quite stable at 4°C and 30°C. At 40°C the half life of the enzyme was 6 h and at 60°C it was 2 h.     

Pretreatment efficiency and structural characterization of rice straw by an integrated process of dilute-acid and steam explosion for bioethanol production

The combined pretreatment of rice straw using dilute-acid and steam explosion followed by enzymatic hydrolysis was investigated and compared with acid-catalyzed steam explosion pretreatment. In addition to measuring the chemical composition, including glucan, xylan and lignin content, changes in rice straw features after pretreatment were investigated in terms of the straw's physical properties. These properties included crystallinity, surface area, mean particle size and scanning electron microscopy imagery. The effect of acid concentration on the acid-catalyzed steam explosion was studied in a range between 1% and 15% acid at 180°C for 2 min. We also investigated the influence of the residence time of the steam explosion in the combined pretreatment and the optimum conditions for the dilute-acid hydrolysis step in order to develop an integrated process for the dilute-acid and steam explosion. The optimum operational conditions for the first dilute-acid hydrolysis step were determined to be 165°C for 2 min with 2% H(2)SO(4) and for the second steam explosion step was to be carried out at 180°C for 20 min; this gave the most favorable combination in terms of an integrated process. We found that rice straw pretreated by the dilute-acid/steam explosions had a higher xylose yield, a lower level of inhibitor in the hydrolysate and a greater degree of enzymatic hydrolysis; this resulted in a 1.5-fold increase in the overall sugar yield when compared to the acid-catalyzed steam explosion.     

Irreversible thermoinactivation of ribonuclease‐A by soft‐hydrothermal processing

Ribonuclease (RNase), which often represents molecular biological contamination, is a thermostable enzyme. When RNase is heated at 121°C by autoclave sterilization for 20 min, it does not lose its activity. However, the nature of the molecular events by which the irreversible denaturation occurs remains unknown. The purpose of this study was to elucidate the molecular mechanisms of irreversible thermal denaturation of RNase A and to develop an advanced sterilization method using soft‐hydrothermal processing, which has the advantages of improved safety and cost‐efficiency. The enzymatic activity of RNase was measured using polyacrylamide gel electrophoresis with torula yeast RNA. We evaluated the temperature and time course of irreversible thermoinactivation of RNase by normal autoclaving, hot‐air sterilization, and soft‐hydrothermal processing that had been controlled to the desired steam saturation ratio. The results indicated that RNase A was deactivated by autoclave sterilization (121°C, 20 min) immediately after treatment, but was reactivated over time. Hot‐air sterilization (180°C, atmospheric pressure, 60 min) produced results similar to that of autoclave sterilization. In contrast, RNase A was irreversibly thermoinactivated by soft‐hydrothermal processing (110°C, 20 min) at 100% steam saturation ratio. We also determined that the mechanism of irreversible thermoinactivation of RNase A involved hydrolysis and deamidation under this condition at a steam saturation ratio of more than 100%. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Steam reforming of bio-oil from rice husks fast pyrolysis for hydrogen production

Steam reforming of two kinds of bio-oil from rice husks fast pyrolysis was conducted for hydrogen production at three temperatures (650, 750 and 850 °C) with Ni-based catalyst in a fixed-bed reactor. The gas composition and organic compounds in liquid condensate were detected by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. In addition, the carbon deposition was also investigated. The results showed that the mole fraction range of hydrogen was within 55.8-61.3% at all temperatures and more hydrogen was produced at the higher temperature. The highest H? efficiency of bio-oil steam reforming was 45.33% when extra water was added. The bio-oil with lower content of chemical compounds has a higher H? efficiency, but its hydrogen volume was less. Analysis of the liquid condensate showed that most of the organic compounds were circularity compounds. The carbon deposition can decrease the bio-oil conversion, and it was easier to form at the temperature of 750 °C.     

Enteric and manure-derived methane and nitrogen emissions as well as metabolic energy losses in cows fed balanced diets based on maize, barley or grass hay

Ruminant husbandry constitutes the most important source of anthropogenic methane (CH4). In addition to enteric (animal-derived) CH4, excreta are another source of CH4, especially when stored anaerobically. Increasing the proportion of dietary concentrate is often considered as the primary CH4 mitigation option. However, it is unclear whether this is still valid when diets to be compared are energy-balanced. In addition, non-structural carbohydrates and side effects on nitrogen (N) emissions may be important. In this experiment, diet types representing either forage-only or mixed diets were examined for their effects on CH4 and N emissions from animals and their slurries in 18 lactating cows. Apart from a hay-only diet, treatments included two mixed diets consisting of maize stover, pelleted whole maize plants and gluten or barley straw and grain and soy bean meal. The diets were balanced in crude protein and net energy for lactation. After adaptation, data and samples were collected for 8 days including a 2-day CH4 measurement in respiratory chambers. Faeces and urine, combined proportionately according to excretion, were used to determine slurry-derived CH4 and N emissions. Slurry was stored for 15 weeks at either 14°C or 27°C, and temperatures were classified as 'cool' and 'warm', respectively. The low-starch hay-only diet had high organic matter and fibre digestibility and proved to be equally effective on the cows' performance as mixed diets. The enteric CH4 formation remained unaffected by the diet except when related to digested fibre. In this case emission was lowest with the hay-only diet (61 v. 88 to 101 g CH4/kg digested NDF). Feeding the hay diet resulted in the highest slurry-CH4 production after 7 weeks of storage at 14°C and 27°C, and after 15 weeks at 14°C. CH4 emissions were, in general, about 10-fold higher at 27°C compared with 14°C but only after 15 weeks of storage. Urinary N losses were highest with the barley diet and lowest with the maize diet. There was a trend towards similar differences in N losses from the slurry of these cows (significant at 14°C). However, contrary to CH4, slurry-N emissions seemed to be temperature-independent. In conclusion, energetically balanced diets proved to be widely equivalent in their emission potential when combining animal and their slurry, this even at a clearly differing forage : concentrate ratio. The variation in CH4 emission from slurry stored shortly or at cold temperature for 15 weeks was of low importance as such conditions did not support methanogenesis in slurry anyway.     

Comparison of sulfuric and hydrochloric acids as catalysts in hydrolysis of Kappaphycus alvarezii (cottonii)

In this study, hydrolysis of marine algal biomass Kappaphhycus alvarezii using two different acid catalysts was examined with the goal of identifying optimal reaction conditions for the formation of sugars and by-products. K. alvarezii were hydrolyzed by autoclave using sulfuric acid or hydrochloric acid as catalyst with different acid concentrations (0.1-1.0 M), substrate concentrations (1.0-13.5%), hydrolysis time (10-90 min) and hydrolysis temperatures (100-130 (°)C). A difference in galactose, glucose, reducing sugar and total sugar content was observed under the different hydrolysis conditions. Different by-product compounds such as 5-hydroxymethylfurfural and levulinic acid were also observed under the different reaction conditions. The optimal conditions for hydrolysis were achieved at a sulfuric acid concentration, temperature and reaction time of 0.2 M, 130 °C and 15 min, respectively. These results may provide useful information for the development of more efficient systems for biofuel production from marine biomass.     

Use of protein microarray to identify gene expression changes of Yersinia pestis at different temperatures

Yersinia pestis is a bacterium that is transmitted between fleas, which have a body temperature of 26 °C, and mammalian hosts, which have a body temperature of 37 °C. To adapt to the temperature shift, phenotype variations, including virulence, occur. In this study, an antigen microarray including 218 proteins of Y. pestis was used to evaluate antibody responses in a pooled plague serum that was unadsorbed, adsorbed by Y. pestis cultivated at 26 °C, or adsorbed by Y. pestis cultivated at 26 and 37 °C to identify protein expression changes during the temperature shift. We identified 12 proteins as being expressed at 37 °C but not at 26 °C, or expressed at significantly higher levels at 37 °C than at 26 °C. The antibodies against 7 proteins in the serum adsorbed by Y. pestis cultivated at 26 and 37 °C remained positive, suggesting that they were not expressed on the surface of Y. pestis in LB broth in vitro or specifically expressed in vivo. This study proved that protein microarray and antibody profiling comprise a promising technique for monitoring gene expression at the protein level and for better understanding pathogenicity, to find new vaccine targets against plague.     

N-terminal purification tag alters thermal stability of the carboxylesterase EstGtA2 from G. thermodenitrificans by impairing reversibility of thermal unfolding

The novel thermostable carboxylesterase EstGtA2 from G. thermodenitrificans (accession no. AEN92268) was functionally expressed and purified using an N-terminal fusion tag peptide. We recently reported general properties of the recombinant enzyme. Here we report preliminary data on thermal stability of EstGtA2 and of its tagged form. Conformational stability was investigated using circular dichroism and correlated with residual activity measurements using a colorimetric assay. The tag peptide had no considerable impact on the apparent melting temperature: T(m) value = 64.8°C (tagged) and 65.7°C (cleaved) at pH 8. After thermal unfolding, the tag-free enzyme rapidly recovered initial activity at 25°C (1.2 Umg(-1)), which was corroborated by substantial refolding (83%) as determined by far-UV CD transitions. However, after thermal unfolding, the purification tag drastically decreased specific activity at 25°C (0.07 Umg(-1)). This was corroborated by the absence of refolding transition. Although the purification tag has no undesirable impact on activity before thermal unfolding as well as on Tm, it drastically hinders EstGtA2 refolding resulting in a major loss of thermal stability.     

耐热荧光素酶的表达及热稳定焦磷酸测序体系的建立

焦磷酸测序是一种基于生物发光反应的实时DNA序列测定技术,其反应体系中的荧光素酶决定测序反应的灵敏度。传统焦测序反应使用的是野生型北美荧光素酶Photinus pyralis luciferase(PpL),该酶热稳定性较差,因此由该酶配制的焦磷酸测序反应体系对热不稳定,影响焦磷酸测序的灵敏度。为了建立热稳定的焦磷酸测序反应体系,全合成了耐热突变日本萤火虫荧光素酶的编码序列,并将其插入到表达载体pET28a(+)中构建重组质粒,将重组质粒转化到大肠杆菌中,筛选得到的阳性重组菌成功表达了N端带有6×His(组氨酸)标签的耐热突变日本萤火虫荧光素酶。利用镍亲和层析法,纯化得到了分子量约为60 kDa且比活为4.29×1010RLU/mg的重组蛋白。对重组耐热日本萤火虫荧光素酶的热稳定性研究结果表明,该酶在50℃时仍具有活性,在40℃下孵育25 min后活性保留了90%以上。与基于野生型北美荧光素酶的焦磷酸测序体系相比,由耐热日本萤火虫荧光素酶配制的测序反应体系对热稳定性有了极大的提高,该测序反应液在37℃放置1 h后仍能够得到正确的测序结果。研究结果为建立稳定可靠的现场及时快速焦磷酸测序反应体系奠定了基础。     

Surface plasmon resonance and NMR analyses of anti Tn-antigen MLS128 monoclonal antibody binding to two or three consecutive Tn-antigen clusters

Tn-antigens are tumour-associated carbohydrate antigens that are involved in metastatic processes and are associated with a poor prognosis. MLS128 monoclonal antibody recognizes the structures of two or three consecutive Tn-antigens (Tn2 or Tn3). Since MLS128 treatment inhibits colon and breast cancer cell growth [Morita, N., Yajima, Y., Asanuma, H., Nakada, H., and Fujita-Yamaguchi, Y. (2009) Inhibition of cancer cell growth by anti-Tn monoclonal antibody MLS128. Biosci. Trends 3, 32-37.], understanding the interaction between MLS128 and Tn-clusters may allow us to the development of novel cancer therapeutics. Although MLS128 was previously reported to have specificity for Tn3 rather than Tn2, similar levels of Tn2/Tn3 binding were unexpectedly observed at 37°C. Thus, thermodynamic analyses were performed via surface plasmon resonance (SPR) using synthetic Tn2- and Tn3-peptides at 10, 15, 20, 25 and 30°C. SPR results revealed that MLS128's association constants for both antigens were highly temperature dependent. Below 25°C MLS128's association constant for Tn3-peptide was clearly higher than that for Tn2-peptide. At 30°C, however, the association constant for Tn2-peptide was higher than that for Tn3-peptide. This reversal of affinity is due to the sharp increase in K(d) for Tn3. These results were confirmed by NMR, which directly measured MLS128-Tn binding in solution. This study suggested that thermodynamic control plays a critical role in the interaction between MLS128/Tn2 and MLS128/Tn3.     

Evaluation of steam explosion pre-treatment for enzymatic hydrolysis of sunflower stalks

Sunflower stalks, a largely available and cheap agricultural residue lacking of economic alternatives, were subjected to steam explosion pre-treatment, the objective being to optimize pre-treatment temperature in the range 180-230°C. Enzymatic hydrolysis performed on the pre-treated solids by a cellulolytic complex (Celluclast 1.5L) and analysis of filtrates were used to select the best pre-treatment temperature. Temperature selection was based on the susceptibility to enzymatic hydrolysis of the cellulose residue and both the cellulose recovery in the solid and the hemicellulose-derived sugars recoveries in the filtrate. After 96h of enzymatic action, a maximum hydrolysis yield of 72% was attained in the water-insoluble fiber obtained after pre-treatment at 220°C, corresponding to a glucose concentration of 43.7g/L in hydrolysis media. Taking into account both cellulose recovery and hydrolysis yield, the maximum value of glucose yield referred to unpretreated raw material was also found when using steam pre-treated sunflower stalks at 220°C, obtaining 16.7g of glucose from 100g of raw material. With regard to the filtrate analysis, most of the hemicellulosic-derived sugars released during the steam pre-treatment were in oligomeric form, the highest recovery being obtained at 210°C pre-treatment temperature. Moreover, the utilisation of hemicellulosic-derived sugars as a fermentation substrate would improve the overall bioconversion of sunflower stalks into fuel ethanol.     

The onset temperature of the heat-shock response and whole-organism thermal tolerance are tightly correlated in both laboratory-acclimated and field-acclimatized tidepool sculpins (Oligocottus maculosus)

We examined the relationship between thermal tolerance, measured as critical thermal maximum (CT(max)), and aspects of the heat-shock response in tidepool sculpins (Oligocottus maculosus) acclimated to constant laboratory temperatures or acclimatized to field conditions. The CT(max) of fish laboratory acclimated to 6°, 13°, and 20°C were 27.6° ± 0.1°C, 29.5° ± 0.1°C, and 30.8° ± 0.1°C, respectively, increasing linearly by 0.2°C for each 1°C increase in acclimation temperature. The CT(max) of field-acclimatized fish from the low intertidal (29.9° ± 0.1°C) was significantly lower than that of fish from the mid- (30.5° ± 0.1°C) and high (30.4° ± 0.1°C) intertidal. CT(max) and the onset temperature of hsp70 induction in gill (T(on)) were highly correlated in both laboratory-acclimated and field-acclimatized sculpins, with T(on) occurring at 2°C below CT(max) in all cases. However, there was no consistent relationship between CT(max) and the maximum levels of gill hsp70 mRNA. Predicted "acclimation" temperature (15.9° ± 0.3°C) and mean habitat temperature (15.9° ± 1.6°C) were similar for sculpins from low intertidal pools, but this relationship was not apparent in mid- and high intertidal fish. Mark-recapture experiments indicated that approximately 80% of fish from low intertidal pools were residents of that pool, but residency rates were less than 50% in mid- and high intertidal pools, which may explain the lack of correlation between CT(max) and habitat variables in these groups. These data indicate that gill hsp70 T(on) and CT(max) are highly correlated indicators of the thermal performance of tidepool sculpins in both laboratory and field settings.     

Can electromagnetic fields influence the structure and enzymatic digest of proteins? A critical evaluation of microwave-assisted proteomics protocols

This study reevaluates the putative advantages of microwave-assisted tryptic digests compared to conventionally heated protocols performed at the same temperature. An initial investigation of enzyme stability in a temperature range of 37-80°C demonstrated that trypsin activity declines sharply at temperatures above 60°C, regardless if microwave dielectric heating or conventional heating is employed. Tryptic digests of three proteins of different size (bovine serum albumin, cytochrome c and β-casein) were thus performed at 37°C and 50°C using both microwave and conventional heating applying accurate internal fiber-optic probe reaction temperature measurements. The impact of the heating method on protein degradation and peptide fragment generation was analyzed by SDS-PAGE and MALDI-TOF-MS. Time-dependent tryptic digestion of the three proteins and subsequent analysis of the corresponding cleavage products by MALDI-TOF provided virtually identical results for both microwave and conventional heating. In addition, the impact of electromagnetic field strength on the tertiary structure of trypsin and BSA was evaluated by molecular mechanics calculations. These simulations revealed that the applied field in a typical laboratory microwave reactor is 3-4 orders of magnitude too low to induce conformational changes in proteins or enzymes.