A Golgi-localized glycosyltransferase, OsGT14;1, is required for growth of both roots and shoots in rice.

Glycosyltransferases (GTs) form a large family in plants and are important enzymes for the synthesis of various polysaccharides, but only a few members have been functionally characterized. Here, through mutant screening with gene mapping, we found that an Oryza sativa (rice) mutant with a short-root phenotype was caused by a frame-shift mutation of a gene (OsGT14;1) belonging to the glycosyltransferase gene family 14. Further analysis indicated that the mutant also had a brittle culm and produced lower grain yield compared with wild-type rice, but the roots showed similar root structure and function in terms of the uptake of mineral nutrients. OsGT14;1 was broadly expressed in all organs throughout the entire growth period, with a relatively high expression in the roots, stems, node I and husk. Furthermore, OsGT14;1 was expressed in all tissues of these organs. Subcellular observation revealed that OsGT14;1 encoded a Golgi-localized protein. Mutation of OsGT14;1 resulted in decreased cellulose content and increased hemicellulose, but did not alter pectin in the cell wall of roots and shoots. The knockout of OsGT14;1 did not affect the tolerance to toxic mineral elements, including Al, As, Cd and salt stress, but did increase the sensitivity to low pH. Taken together, OsGT14;1 located at the Golgi is required for growth of both roots and shoots in rice through affecting cellulose synthesis.

Plastic transport systems of rice for mineral elements in response to diverse soil environmental changes.

Climate change will increase frequency of drought and flooding, which threaten global crop productivity and food security. Rice (Oryza sativa) is unique in that it is able to grow in both flooded and upland conditions, which have large differences in the concentrations and chemical forms of mineral elements available to plants. To comprehensively understand the mechanisms of rice for coping with different water status, we performed ionomics and transcriptomics analysis of the roots, nodes and leaves of rice grown in flooded and upland conditions. Focusing the analysis on genes encoding proteins involved in transport functions for mineral elements, it was found that, although rice plants maintained similar levels of each element in the shoots for optimal growth, different transporters for mineral elements were utilised for nitrogen, iron, copper and zinc to deal with different soil water conditions. For example, under flooded conditions, rice roots take up nitrogen using transporters for both ammonium (OsAMT1/2) and nitrate (OsNPF2.4, OsNRT1.1A and OsNRT2.3), whereas under upland conditions, nitrogen uptake is mediated by different nitrate transporters (OsNRT1.1B and OsNRT1.5A). This study shows that rice possesses plastic transport systems for mineral elements in response to different water conditions (upland and flooding).

Method for automatically identifying spectra of different wood cell wall layers in Raman imaging data set.

The technique of Raman spectroscopic imaging is finding ever-increasing applications in the field of wood science for its ability to provide spatial and spectral information about the sample. On the basis of the acquired Raman imaging data set, it is possible to determine the distribution of chemical components in various wood cell wall layers. However, the Raman imaging data set often contains thousands of spectra measured at hundreds or even thousands of individual frequencies, which results in difficulties accurately and quickly extracting all of the spectra within a specific morphological region of wood cell walls. To address this issue, the authors propose a new method to automatically identify Raman spectra of different cell wall layers on the basis of principal component analysis (PCA) and cluster analysis. A Raman imaging data set collected from a 55.5 µm × 47.5 µm cross-section of poplar tension wood was analyzed. Several thousand spectra were successfully classified into five groups in accordance with different morphological regions, namely, cell corner (CC), compound middle lamella (CML), secondary wall (SW), gelatinous layer (G-layer), and cell lumen. Their corresponding average spectra were also calculated. In addition, the relationship between different characteristic peaks in the obtained Raman spectra was estimated and it was found that the peak at 1331 cm(-1) is more related to lignin rather than cellulose. Not only can this novel method provide a convenient and accurate procedure for identifying the spectra of different cell wall layers in a Raman imaging data set, but it also can bring new insights into studying the morphology and topochemistry in wood cell walls.

[Study of alkaline lignin from Arundo donax linn based on FT Raman spectroscopy].

Arundo donax linn, as a perennial energy crop, has promising application prospect. In the present study, Fourier transform Raman (FT Raman) spectroscopy was applied to determine the structural information of materials, milled wood lignin (MWL), and alkaline lignins (AL, under different treated time) from A. donax stem nondestructively. The results indicated that, extractable compounds in A. donax had negative contribution to the Raman spectra without rising new Raman peaks. FT Raman spectrum of MWL indicated that MWL from A. donax was HGS type lignins. Compared with the spectra of MWL from wood materials, the peak at 1173 cm(-1) was much higher in intensity for the MWL from A. donax stem, which may be assigned to hydroxycinnamic acid by analyzing the standard. With respect to FT Raman spectra of ALs, the relatively highest intensity of 1173 cm(-1) was found in alkaline lignin (AL2), which was treated for 40 min by alkaline. Moreover, the peak of coniferaldehyde/sinapaldehyde (1630 cm(-1)) was lowest in intensity while the band attributed to coniferyl alcohol/sinapyl alcohol (1660 cm(-1)) was almost disappeared in AL2. It could be inferred that AL2 demonstrated a highest content of phenolic acid, which may improve its potential application, such as for antioxidant activity. Furthermore, the results obtained by FT Raman spectra were verified by two dimensional heteronuclear singlequantum coherence nuclear magnetic resonance analyses. Above all, FT Raman spectroscopy provided alternative safe, rapid, accurate, and nondestructive technology for lignin structure determination.

Enhancing fuel characteristics and combustion performance of cellulose-rich straws through CO2-assisted torrefaction.

Cellulose-rich straws of corn and rice were torrefied under carbon dioxide, and the fuel characteristics and combustion performance of the obtained biochar were investigated. A high severity resulted in surface collapse, greater pore volume, elimination of oxygen, elevated calorific value, and improved hydrophobicity in biochar. Following carbon dioxide torrefaction, the cellulose content in solid biochar experienced a slight decrease when the temperature was raised to 220 °C for longer residence durations. At 300 °C, the cellulose content in the biochar was nearly eliminated, while the relative proportion of non-sugar organic matter in corn stover and rice straw increased to 87.40 % and 77.27 %, respectively. The maximum calorific values for biochar from corn and rice straws were 22.38 ± 0.03 MJ/kg and 18.72 ± 0.05 MJ/kg. The comprehensive combustion indexes of rice and corn straw samples decreased to 1.06 × 10-7 and 1.31 × 10-7 after torrefaction at 300 °C, respectively. In addition, the initial decomposition temperatures increased by 38 °C and 45 °C, while the ultimate combustion temperatures rose by 13 °C and 16 °C for corn and rice straws, respectively. These results imply an extended combustion timeframe for the torrefied samples.

[Application of the Raman spectroscopy to the study of plant cell walls].

Due to the deficiency of energy supply and negative environmental impacts. Much attentions have been paid to agnicultural these lignocellulosic the replacement of fossil resources with and forestry biomass for the production of bio-fuels, chemicals and biomaterials on a global scale. Highly effective utilization of biomass is dependent on full understanding of their chemical composition and structural characteristics. A state-of-the-art Raman spectroscopy has evolved an important and nondestructive technique for plant research as information concerning histochemistry and structural characteristics of plant cell walls can be investigated in a nearly native state. In this paper, the principle of Raman imaging was introduced briefly. Meanwhile, the research progress in structural analysis of major components, micro-area distribution and molecular organization of the cellulose and lignin in the plant cell walls by Raman spectroscopy was summarized. The aim of the review is to promote the application of Raman spectroscopy to the study of plant cell walls.

Effect of silicon deficiency on secondary cell wall synthesis in rice leaf.

Rice (Oryza sativa L.) is a typical Si-accumulating plant and is able to accumulate Si up to >10 % of shoot dry weight. The cell wall has been reported to become thicker under Si-deficient condition. To clarify the relationship between Si accumulation and cell wall components, the physical properties of, and macromolecular components and Si content in, the pectic, hemicellulosic, and cellulosic fractions prepared from rice seedlings grown in hydroponics with or without 1.5 mM silicic acid were analyzed. In the absence of Si (the -Si condition), leaf blades drooped, but physical properties were enhanced. Sugar content in the cellulosic fraction and lignin content in the total cell wall increased under -Si condition. After histochemical staining, there was an increase in cellulose deposition in short cells and the cell layer just beneath the epidermis in the -Si condition, but no significant change in the pattern of lignin deposition. Expression of the genes involved in secondary cell wall synthesis, OsCesA4, OsCesA7, OsPAL, OsCCR1 and OsCAD6 was up-regulated under -Si condition, but expression of OsCesA1, involved in primary cell wall synthesis, did not increase. These results suggest that an increase in secondary cell wall components occurs in rice leaves to compensate for Si deficiency.

[Confocal Raman microspectroscopy study on the distribution of cellulose and lignin in Daphne odora Thunb].

Confocal Raman microspectroscopy is well suited to investigating cellulose and lignin distribution in-situ in the native cell walls of woody tissue. In this study, transmission electron microscopy (TEM) was used to determine the ultrastructure of Daphne odora Thunb. In the TEM images, cell wall of Daphne odora Thunb. is typically divided into three layers: middle lamellar (ML), primary wall (P) and secondary wall (S1, S2 and S3). More detailed information about cellulose and lignin distribution in different cell wall layers was analyzed in situ by confocal Raman microspectroscopy. Raman spectra and images reveal that the distribution of cellulose and lignin in the cell wall layers is not uniform. Lignin concentration in different morphological areas follows the decreasing order: the cell corner (CC) > the middle lamellar (CML) > the secondary wall (S2). In contrast, cellulose distribution shows the opposite pattern-low concentration in CC and CML and high in S2 regions.

Flow-through strategy to fractionate lignin from eucalyptus with formic acid/hydrochloric solution under mild conditions.

Formic acid is an attractive solvent for the fractionation of lignocellulose for the production of biomaterials and chemicals, while the operation conducted in a batch manner is not conducive to mass transfer in separation process. In this research, eucalyptus was fractionated with formic acid/hydrochloric solution in a flow-through reactor at 95 °C, and the structural characteristics and the composition of fractionated lignin in different stages were investigated. Results showed that the fractionation efficiency was notably improved with a flow-through reactor, as evidenced by the low solid residue yield of 49.5% and the lignin removal rate of 79.4% as compared to the batch manner. During the fractionation process, the dissolution rate of lignin decreased gradually, and the obtained lignin samples showed low molecular weight (<3000), good uniformity (<2), and high thermal stability. The structure analysis showed that ß-O-4, ß-ß, and ß-5 linkages in lignin were degraded to varying degrees with increased time, and the degradation of G units was more severe than S ones.

[Effect of sintering temperature on mechanical properties of dental zirconia toughened alumina ceramics].

PURPOSE: To investigate the effect of sintering temperature on mechanical properties of dental zirconia toughened alumina (ZTA) ceramics prepared by gel-casting technique. METHODS: The samples prepared by gel-casting were sintered at 1100, 1200, 1250, 1300 and 1400degrees centigrade for each group. The flexural strength, fracture toughness, Vickers hardness and brittleness index were obtained and microscopic morphology of each group was observed under scanning electron microscope (SEM). The data were statistically analyzed using SPSS 19.0 software package. RESULTS: The flexural strength, fracture toughness and Vickers hardness increased with the increasing sintering temperature during 1100~1400degrees centigrade. The lowest brittleness index (0.74±0.16) µm-1/2 was observed in group sintered at 1200degrees centigrade and the highest (2.76±0.14) µm-1/2 was at 1400degrees centigrade (P<0.05), while the flexural strength of these two groups was (46.89±3.24) MPa and (349.64±54.72) MPa, respectively. CONCLUSIONS: The ZTA dental ceramics exhibit good machinability with proper sintering temperature (1200degrees centigrade) and the strength meets the requirement of clinical application.

Structural modification of hemicelluloses and lignin based on the biorefinery process with white-rot fungal.

On the concept of biorefinery, hemicellulosic and lignin fractions were isolated from white-rot fungal Trametes velutina D10149 biodegraded poplar, and the structural modification was elucidated in detail according to the different incubation duration. Transversal-section Raman images showed that the fiber secondary walls were preferentially degraded, whereas the compound middle lamellae, including the cell corner regions, were mainly intact after 16 weeks incubation. More importantly, lignin and carbohydrates were simultaneously removed within the fiber secondary wall. From wet chemistry analysis, the yields and structural properties for both hemicellulosic and lignin fractions were not significantly altered. The synergistic effect of ligninolytic system finally obviously appeared after 16 weeks incubation, evidenced by the remarkable decrement of hemicellulose and lignin molecular weights. Additionally, the preferential degradation of S units in lignin biomacromolecule was further confirmed by composition analysis of cell wall phenolics and the integration of 2D NMR correlations in the aromatic region.

[Comparison of the shear bond strength by using nano silica sol to zirconia basement and veneer porcelain].

PURPOSE: To investigate the feasibility of using sol gel technique to produce thin layer nano silicon dioxide on zirconia ceramic surface and the effect of improving shear bond strength between zirconia and veneer porcelain. METHODS: The presintered zirconia specimen was cut into a rectangle block piece (15 mm×10 mm×2.5 mm), a total of 40 pieces were obtained and divided into 4 groups, each group had 10 pieces. Four different treatments were used in each group respectively. Pieces in group A (control group) were only sintered at 1450°C to crystallization; pieces in group B underwent 30% nano silica sol infiltration first and then were sintered at 1450°C to crystallization; piece in group C underwent crystallization first at 1450°C, then 30% nano silica sol infiltration and were sintered at 1450°C again; pieces in group D was coated by nano silica sol and then sintered at 1450°C to crystallization; ten rectangle block pieces (12 mm×8 mm×2 mm) in group E were made. Cylinder veneers 5 mm in diameter and 4 mm in height were produced in each group and the shear bond strength was tested. Data were statistically analyzed by SPSS 19.0 software package. RESULTS: The shear bond strength of the 5 group specimens were: (28.12±2.95) MPa in group A, (31.09±3.94) MPa in group B, (25.60±2.45) MPa in group C, (31.75±4.90) MPa in group D, (28.67±3.95) MPa in group E, respectively. Significant differences existed between the 5 groups, and group C had significant difference compared with group B and D. CONCLUSIONS：① Use of nano silicon sol gel on presintered zirconia surface to make thin layer of nano silicon dioxide can improve the shear bond strength between zirconia and veneer; ②Using nano silicon sol gel on crystallization zirconia surface to make thin layer of nano silicon dioxide will decrease the shear bond strength between zirconia and veneer; ③ Zirconia veneer bilayer ceramic has the same shear bond strength with porcelain fused to Ni Cr alloy; ④Use of sol gel technique to produce thin layer nano silicon dioxide on zirconia ceramic surface is feasible and can improve shear bond strength between zirconia and veneer porcelain.

Effect of dehydration time on tooth colour measurement in vitro.

OBJECTIVE: To investigate the effect of dehydration time on tooth colour measurement in vitro using colourimetry. METHODS: Ten extracted human maxillary central incisors were used. L*a*b* values at the centre of the labial surface of each tooth were measured using a colourimeter. The first measurement was performed after removal of excess water. The second and third measurements were performed after the teeth had dried at room temperature for 2 h and 4 h, respectively. The colour differences (ΔE) between dehydration time points were calculated. Repeated oneway ANOVA was performed for colour values at different dehydration time points. Pairwise comparison of group means (Student t test) was used to examine the differences between ΔE and 1.5ΔE (α = 0.05). RESULTS: There were statistically significant changes in the L* values after 2 h and 4 h dehydration as well as between each ΔE and 1.5ΔE. Neither 2 h nor 4h dehydration resulted in change of a* value or b* value. CONCLUSION: Dehydration time affected colour measurement using a colourimeter; the teeth become lighter after dehydration for 2 h or longer.

[Influence of La2O3 and Li2O on glass powder for infiltrating ZTA all-ceramic dental material formed by gel-casting].

PURPOSE: The influence of La2O3 and Li2O on glass powder was studied in this paper, which is to infiltrate ZTA all-ceramic dental material formed by gel-casting. The performance of different component was analyzed to optimize glass formula. METHODS: Six groups of glass powder were designed and prepared by conventional melt-quenching method. ZTA ceramic blocks were covered with glass paste, which were formed by gel-casting and sintered in 1200 degrees centigrade, then infiltrated in 1150 degrees centigrade for twice to make glass/ZTA ceramic composites. By detecting differential thermal analysis and melting range of infiltration glass power, as well as flexural strength, linear shrinkage, SEM and EDS of glass/ZTA ceramic composites, the optimized glass group was determined out. Statistical analysis was performed using SPSS 13.0 software package by means of paired t test or one way ANOVA. RESULTS: The bending strength of group Li1 was (291.2±27.9) MPa, significantly higher than group Li2 and group La2(P<0.05), and linear shrinkage of group Li1 was only(1.85±0.27)%. SEM and EDS showed glass of group Li1 can lubricate ZTA ceramics well, their structure was compact and had a few small pores. Intergranular fracture existed on cross surface as well as transgranular fracture. CONCLUSIONS: The results showed that Li1(30%La2O3-15%Al2O3-15%SiO2-15%B2O3-5%Li2O) glass infiltrated ZTA ceramic composite had the best capability. Glass/ZTA composite material can be prepared by gel-casting and infiltrating way, and this process is simple and economically suitable for general dental laboratory.

[An anticaries experimental study of SD rat immunized by recombinant plasmid pEGFP-N1-Srv+ encoding the V-region of surface protein of Streptococcus mutans].

PURPOSE: An anticaries DNA vaccine pEGFP-N1-Srv+ was used to immunize rats by different immune pathways. The expression of recombinant plasmid in different tissues in vivo and the specific immune response and protection effects against dental caries were observed. METHODS: 20 SD rats were divided into 4 groups, immunized with the recombinant plasmid pEGFP-N1-SrV+ by submandibular gland-target injection(TSG), and intramuscular injection,respectively; then the expression of recombinant plasmid in different tissues were detected by immunohistochemistry technique. 24 SD rats were divided into 4 groups, immunized with recombinant plasmid pEGFP-N1-SrV+ of 100 µg, then boosted once after two weeks, through the same routes as above;then indirect ELISA technique was used to detect the specific antibodies. Keyes caries scores were used to evaluate the anticaries effects. The data was analyzed by using SPSS17.0 software package. RESULTS: (1)Recombinant plasmid was positively expressed in the muscle fibers and submandibular glands.(2)The specific salivary anti-SR IgA and serum IgG were detected, and the peak time of the antibodies level appeared 4 weeks after initial . At the 4th week, the levels of specific anti-SR antibodies were higher in the experimental group than that in the negative control group. The levels of salivary specific anti-SR IgA were significantly higher in TSG immunization group than that in the intramuscular injection group. (3)Keyes caries scores were not significantly different between the experimental groups and negative control groups. recombinant plasmid pEGFP-N1-Srv+ expressed in vivo and effectively increased specific salivary anti-SR IgA and serum IgG, and TSG immunization route significantly increased the specific salivary anti-SR IgA compared with the intramuscular immunization route;however, the recombinant plasmid pEGFP-N1-Srv+ alone can not protect the rats from dental caries. CONCLUSIONS: The recombinant plasmid pEGFP-N1-SrV+ expressed in vivo and effectively increased specific salivary anti-SR IgA and serum IgC, and TSG immunization route significantly increased the specific salivary anti-SR IgA compared with the intramuscular immunization route; however, the recombinant plasmid pEGFP-N1-Srv+ alone can not protect the rats from dental caries.

[Effect of beryllium on chemical elements of cell membrane and H2O2 production of Streptococcus oralis].

PURPOSE: To evaluate the effect of beryllium (Be(2+)) on chemical elements of cell membrane and H2O2 production of Streptococcus oralis (S.oralis), thus to explore the microbiologic mechanisms of periodontal diseases which may occur after prosthodontic treatment. METHODS: S.oralis was put into artificial saliva with different Be(2+) concentration (5mg/L, 10mg/L, 20mg/L and 40mg/L) and anaerobic cultured for 24 hours. The amount of chemical elements in the membrane of S.oralis were tested with X-ray energy dispersive spectroscopy, and the H(2)O(2) produced by S.oralis was detected with ABTS-HRP. The data were analyzed with one-way ANOVA using SPSS 11.0 software package. RESULTS: The amount of calcium in the cell membrane of beryllium treated S. oralis decreased, while the amount of phosphorus increased. Natrium increased with the increase of Be(2+) in the culture, but changed contrarily when S. oralis was treated with 20mg/L Be(2+). H(2)O(2) produced by S. oralis reduced when the concentration of Be(2+) was at 40mg/L(P<0.05). CONCLUSIONS: Beryllium affects the amount of chemical elements in cell membrane and H(2)O(2) production of S. oralis, which may result in a disturbance in the microecologic balance of subgingival microbes after proshodontic treatments and eventually contribute to periodontal diseases.

Effects of background, direction and intensity of ambient light, measuring position, and adjacent teeth, on anterior tooth colour measurement in vitro.

OBJECTIVE: to investigate the effects of different background colours (black, white or pink), direction and intensity of ambient light, measuring position, and the adjacent teeth, on the in vitro colour measurement of maxillary anterior teeth, using the Minolta CR-321 colorimeter. METHODS: ten extracted human maxillary central incisors were selected. A fibre-optic light MI-150 was used as the ambient illuminant. Teeth were irradiated from a 3- or 12-o'clock direction. L*a*b* values of seven sites on the labial surfaces were obtained by means of the Minolta CR-321 colorimeter, using three background colours, with or without the adjacent teeth. The recorded data were analysed with two-tailed Student t tests and analysis of variance (α = 0.05). RESULTS: the ambient light did not affect the colour measurement of anterior teeth, regardless of the presence or absence of the adjacent teeth. There were no statistically significant differences in L*a*b* values at the same position under different background colours, except ΔE12 (colour difference between site 1 and site 2) between black and white backgrounds. ΔE12 (under black background), ΔE13 and ΔE15 were greater than 1.5, while the others were lower than 1.5. CONCLUSION: the background, ambient light and the presence of adjacent teeth did not affect the colour measurement of anterior teeth using the Minolta CR-321 colorimeter in vitro. The inherent disadvantages of using the naked eye during clinical visual shade assessment may be overcome by the colorimeter.

[Influence of MgO and TiO2 on mechanical properties of zirconia toughened alumina ceramics formed by gel-casting technique].

OBJECTIVE: The objective of this study is to investigate the influence of mechanical properties and sintering performance by adding 5% weight percentage aids to nano-compound zirconia toughened alumina (ZTA) ceramics. METHODS: Micrometer Al2O3 and nanometer ZrO2 (quality ratio 4:1) were used to get 55% volume percentage slurry. Magnesium oxide and titanium oxide were taken as aids which were 5% weight percentage of the Al2O3 and ZrO2 powder. Five groups (number 0, 1, 2, 3, 4 group) were divided according to different proportion of aids. After gel-casting, the porcelain pieces were sintered at 1150, 1200, 1300, 1400, 1450, 1500, 1600 degrees C for 2 hours. Static three-point flexure strength, line shrinkage, relative density were measured and scanning electron microscopy (SEM) was used to observe section. RESULTS: Number 1 (MgO 1%, TiO2 4%) group had the highest bending strength. It was (401.78+/-19.50) MPa after sintering at 1600 degrees C for 2 hours and was higher than 0 group (380.64+/-44.50) MPa. Bending strength became lower than 0 group when MgO was more than 2% or more than that weight percentage of ZTA powder. When MgO content was higher than 2% or more than that weight percentage, there was no difference in relative density raising rate between each sintering assistants groups. When the sintering temperature was higher than 1200 degrees C, all groups showed obvious line-shrinkage and the groups which contained sintering assistants were all was higher than 0 group. CONCLUSION: Adding MgO and TiO2 aids from 1% to 4% weight percentage of ZTA will promote fritting and increase ZTA nano-compound ceramics mechanical properties. Adding 2% MgO aids or more than that weight percent will has no obvious help to increase the relative density raising rate of ZTA nano-compound ceramics and will degrade the mechanical properties of ZTA nano-compound ceramics.

Characterization of substrate specificity of a rice silicon transporter, Lsi1.

Lsi1 (OsNIP2;1) is the first silicon (silicic acid) transporter identified in plant, which belongs to the nodulin 26-like intrinsic membrane protein (NIP) subfamily. In this study, we characterized the function of this transporter by using the Xenopus laevis oocyte expression system. The transport activity of Lsi1 for silicic acid was significantly inhibited by HgCl2 but not by low temperature. Lsi1 also showed an efflux transport activity for silicic acid. The substrate specificity study showed that Lsi1 was able to transport urea and boric acid; however, the transport activity for silicic acid was not affected by the presence of equimolar urea and was decreased only slightly by boric acid. Furthermore, among the NIPs subgroup, OsNIP2;2 showed transport activity for silicic acid, whereas OsNIP1;1 and OsNIP3;1 did not. We propose that Lsi1 and its close homologues form a unique subgroup of NIP with a distinct ar/R selectivity filter, which is located in the narrowest region on the extra-membrane mouth and govern the substrate specificity of the pore.

[Influence of ambient light and adjacent tooth in anterior tooth color measurement].

OBJECTIVE: To investigate the influence of different intensity and directions of ambient light and adjacent tooth in anterior tooth color measurement by using colorimeter. METHODS: Fiber lite MI-150 was used as ambient illuminant and it irradiated from three or twelve o'clock direction through 45 degrees angle above. The light magnitude 0, 50, 75, 100, 125, 150 W were applied in this experiment. The values of CIE L* a* b* were measured by Minolta Chroma meter CR-321 colorimeter on the center labial surface of ten extracted human maxillary central incisors with or without adjacent teeth, then those data were analyzed statistically by using SPSS 11.5. RESULTS: Neither different intensities nor different directions of ambient light could influence the results of color measurement by using Minolta Chroma meter CR-321 colorimeter, so did the adjacent teeth whether those were exist or not. CONCLUSION: There is no influence of ambient light and adjacent teeth in the color measurement of anterior teeth under this experiment condition, and Minolta Chroma meter CR-321 colorimeter can be used to measure the color directly aside the chair with light.