Fast and Robust Quantification of Detergent Micellization Thermodynamics from Isothermal Titration Calorimetry.

Detergents are widely used in modern in vitro biochemistry and biophysics, in particular to aid the characterization of integral membrane proteins. An important characteristic of these chemicals in aqueous solutions is the concentration above which their molecular monomers self-associate to form micelles, termed the critical micellar concentration (CMC). Micelles are supramolecular assemblies arranged with the hydrophobic portions oriented inward and the hydrophilic head groups positioned outward to interact with the aqueous solvent. Knowledge of the CMC is not only of practical relevance but also of theoretical interest because it provides thermodynamic insights. Isothermal titration calorimetry (ITC) is a powerful method to determine CMCs, as it furnishes additional information on the enthalpy and entropy of micellization. Here we describe our extension of previous methods to determine CMCs and other thermodynamic parameters from ITC demicellization curves. The new algorithm, incorporated into the stand-alone software package D/STAIN, analyzes ITC demicellization curves by taking advantage of state-of-the-art thermogram-integration techniques and automatically providing rigorous confidence intervals on the refined parameters. As a demonstration of the software's capabilities, we undertook ITC experiments to determine the respective CMCs of n-octyl ß-d-glucopyranoside (OG), n-dodecyl ß-d-maltopyranoside (DDM), and lauryldimethylamine N-oxide (LDAO). Motivated by the fact that in vitro membrane protein studies often require additives such as precipitants (e.g., polyethylene glycol (PEG)), we also carried out ITC demicellization studies in the presence of PEG3350, finding in all cases that PEG had significant effects on the thermodynamics of detergent micellization.

Glass Transition Dynamics and Physical Stability of Amorphous Griseofulvin in Binary Mixtures with Low-Tg Excipients.

Amorphization of drug formulations containing active pharmaceutical ingredients (APIs) and excipients has been proven to be an effective strategy to improve their poor aqueous solubility. The excipients can also impact the physical stability of the prepared amorphous forms. Generally, researchers are more apt to select excipients that have high values of glass transition temperature (Tg) because of the antiplasticization effect of the additives on APIs. In this article, we studied the glass transition dynamics as well as crystallization behavior in binary blends composed of griseofulvin (GSF) and two low-Tg additives, octaacetylmaltose (acMAL) and polyvinyl acetate (PVAc), with a particular focus on the plasticization effect. Effectively suppressed crystallization of GSF is observed in both systems when higher excipient contents are used. Our finding aims to encourage the use of specifically developed protocols in which suitable plasticizers are used as excipients for stabilizing the amorphous state of a drug.

Poly(propylene imine) dendrimers with histidine-maltose shell as novel type of nanoparticles for synapse and memory protection.

Poly(propylene imine) dendrimers have been shown to be promising 3-dimensional polymers for the use in the pharmaceutical and biomedical applications. Our aims of this study were first, to synthesize a novel type of dendrimer with poly(propylene imine) core and maltose-histidine shell (G4HisMal) assessing if maltose-histidine shell can improve the biocompatibility and the ability to cross the blood-brain barrier, and second, to investigate the potential of G4HisMal to protect Alzheimer disease transgenic mice from memory impairment. Our data demonstrate that G4HisMal has significantly improved biocompatibility and ability to cross the blood-brain barrier in vivo. Therefore, we suggest that a maltose-histidine shell can be used to improve biocompatibility and ability to cross the blood-brain barrier of dendrimers. Moreover, G4HisMal demonstrated properties for synapse and memory protection when administered to Alzheimer disease transgenic mice. Therefore, G4HisMal can be considered as a promising drug candidate to prevent Alzheimer disease via synapse protection.

Expression and purification of functionally active ferrous iron transporter FeoB from Klebsiella pneumoniae.

The acquisition of ferrous iron (Fe2+) is an important virulence factor utilized by several hospital-acquired (nosocomial) pathogens such as Klebsiella pneumoniae to establish infection within human hosts. Virtually all bacteria use the ferrous iron transport system (Feo) to acquire ferrous iron from their environments, which are often biological niches that stabilize Fe2+ relative to Fe3+. However, the details of this process remain poorly understood, likely owing to the few expression and purification systems capable of supplying sufficient quantities of the chief component of the Feo system, the integral membrane GTPase FeoB. This bottleneck has undoubtedly hampered efforts to understand this system in order to target it for therapeutic intervention. In this study, we describe the expression, solubilization, and purification of the Fe2+ transporter from K. pneumoniae, KpFeoB. We show that this protein may be heterologously overexpressed in Escherichia coli as the host organism. After testing several different commercially-available detergents, we have developed a solubilization and purification protocol that produces milligram quantities of KpFeoB with sufficient purity for enzymatic and biophysical analyses. Importantly, we demonstrate that KpFeoB displays robust GTP hydrolysis activity (kcatGTP of ∼10-1 s-1) in the absence of any additional stimulatory factors. Our findings suggest that K. pneumoniae may be capable of using its Feo system to drive Fe2+ import in an active manner.

Purification and Characterization of Lipase Produced by Leuconostoc mesenteroides Subsp. mesenteroides ATCC 8293 Using an Aqueous Two-Phase System (ATPS) Composed of Triton X-100 and Maltitol.

Purification of lipase produced by L. mesenteroides subsp. mesenteroides ATCC 8293 was conducted for the first time using a novel aqueous two-phase system (ATPS) composed of Triton X-100 and maltitol. The partitioning of lipase was optimized according to several parameters including pH, temperature, and crude load. Results showed that lipase preferentially migrated to the Triton X-100 rich phase and optimum lipase partitioning was achieved in ATPS at TLL of 46.4% and crude load of 20% at 30 °C and pH 8, resulting in high lipase purification factor of 17.28 and yield of 94.7%. The purified lipase showed a prominent band on SDS-PAGE with an estimated molecular weight of 50 kDa. The lipase was stable at the temperature range of 30⁻60 °C and pH range of 6⁻11, however, it revealed its optimum activity at the temperature of 37 °C and pH 8. Moreover, lipase exhibited enhanced activity in the presence of non-ionic surfactants with increased activity up to 40%. Furthermore, results exhibited that metals ions such as Na⁺, Mg2+, K⁺ and Ca2+ stimulated lipase activity. This study demonstrated that this novel system could be potentially used as an alternative to traditional ATPS for the purification and recovery of enzymes since the purified lipase still possesses good process characteristics after undergoing the purification process.

Interactions of Nitroxide-Conjugated and Non-Conjugated Glycodendrimers with Normal and Cancer Cells and Biocompatibility Studies.

Poly(propyleneimine) glycodendrimers fully modified with maltose units were administered to different cancer cell lines and their effect on cell viability was evaluated by using MTS assay and flow cytometry. The mechanism of dendrimer-cell interactions was investigated by the electron paramagnetic resonance (EPR) technique by using a new nitroxide-conjugated glycodendrimer. The nitroxide groups did not modify both the biological properties (cell viability and apoptosis degree) of the dendrimers in the presence of the cells and the dendrimer-cell interactions. Since this class of dendrimers is already known to be biocompatible for human healthy cells, noncancer cells such as human peripheral blood mononuclear cells (PBMCs) and macrophages were also treated with the glycodendrimer, and EPR spectra of the nitroxide-conjugated glycodendrimer were compared for cancer and noncancer cells. It was found that this dendrimer selectively affects the cell viability of tumor cells, while, surprisingly, PBMC proliferation is induced. Moreover, H-bond-active glycodendrimer-cell interactions were different for the different cancer cell lines and noncancer cells. The nitroxide-conjugated glycodendrimer was able to interact with the cell membrane and eventually cross it, getting in contact with cytosol antioxidants. This study helps to clarify the potential anticancer effect of this class of dendrimers opening to future applications of these macromolecules as new antitumor agents.

Mechanisms of Internalization of Maltose-Modified Poly(propyleneimine) Glycodendrimers into Leukemic Cell Lines.

Poly(propyleneimine) dendrimers of fourth generation partially modified with maltose (open shell structure, PPI-m OS) have been proposed as carriers for nucleotide anticancer drugs. The aim of this work was to provide basic insight into interactions between fluorescently labeled PPI-m dendrimer and two distinct leukemia cell models: CCRF-1301 lymphoid cell line and HL-60 myeloid cell line. We applied qualitative confocal imaging and quantitative flow cytometry, as well as trypan blue quenching and pharmacological inhibition, to investigate the course, kinetics, and molecular mechanisms of internalization of nanoparticles. CCRF-1301 cells take up glycodendrimer macromolecules via a relatively slow, adsorptive endocytosis process, which is cholesterol-dependent, clathrin- and caveolin-independent, and not followed by recycling or exocytosis. Morphological features of this phenomenon point to the involvement of aggregation-induced cell polarity changes (capping). In HL-60 cells, internalization is very fast, independent of binding to the cell surface, and proceeds from the fluid phase via a classical clathrin-dependent mechanism, ending up in an endolysosomal compartment from which it is not further released. This substantial difference in internalization rate and mechanism between two cell types has important repercussions for potential application of this class of glycodendrimers as drug delivery agents.

EFFECTS OF SHORT-TERM USE OF XYLITOL CHEWING GUM AND MOLTITOL ORAL SPRAY ON SALIVARY STREPTOCOCCUS MUTANS AND ORAL PLAQUE.

The purpose of this study was to investigate the short-term effects of xylitol chewing gum and maltitol spray on the concentration of salivary mutans streptococci (MS) and on the plaque index. Eighty-one second, third and fourth year dental and dental assistant students with a salivary MS concentration > 103 CFU/ml cultured on mitis salivarius bacitracin (MSB) agar were included in the study. The age range of subjects was 18-23 years. The participants were divided into 3 groups: control, xylitol chewing gum and maltitol spray groups. Each subject brushed their teeth with fluoridated toothpaste (1,000 ppm). Each subject in the xylitol chewing gum group was told to chew 2 pieces, 6 times a day (total xylitol dose=7.3 g/day) for 4 weeks. Each subject in the maltitol spray group was told to spray one puff twice daily (morning and evening) for 4 weeks. A dental examination and saliva samples to determine the salivary MS concentration were collected at baseline and at 2 and 4 weeks after experiment initiation. The nonparametric Mann­Whitney U test was used to analyze differences among groups. The mean ages in the control, xylitol chewing gum and maltitol spray groups were 22±1, 20±1 and 20±1 years, respectively. The mean MS concentrations at the beginning of the study and after 2 weeks in the control, and xylitol chewing gum and moltitol oral spray groups were not significantly different from each other. There was a significantly lower MS concentration in the moltitol oral spray group than in the control group by 4 weeks (p=0.045) but no significant difference between the control group and the xylitol gum group by 4 weeks. There were no significant differences in the mean plaque index at baseline among the control group, the xylitol chewing gum group and the moltitol oral spray group. The plaque index was significantly lower in the xylitol chewing gum group than the control group (p=0.003) at 2 weeks but not 4 weeks. There was no significant difference in the mean plaque index between the control group and the moltitol oral spray group at any time. Using the maltitol spray significantly reduced the MS level in the saliva by 4 weeks use but using the xylitol gum did not. However, using the xylitol chewing gum did reduce the mean plaque by 2 weeks use but the effect did not last; by 4 weeks there was no difference from control. The moltitol spray provided no benefit over the control in reducing the mean plaque index.

Effects of sugar-free chewing gum sweetened with xylitol or maltitol on the development of gingivitis and plaque: a randomized clinical trial.

OBJECTIVE: The objective of this study was to test the effect of sugar-free chewing gum sweetened with xylitol or maltitol compared to the use of a gum base or no gum on gingivitis and plaque scores under both brushing and non-brushing circumstances. METHODS: The design of the study was a four-group, double-blinded, randomized controlled study with a 3-week duration. In each group, the participants did not brush the teeth in the lower jaw designated to develop experimental gingivitis, while maintaining normal oral hygiene procedures in the upper jaw. After professional dental prophylaxis, the participants were allocated into one of four groups (xylitol, maltitol, gum base or no gum). Chewing gum was used five times a day for 10 min. RESULTS: 220 participants completed the study and provided evaluable data. The increase in bleeding on marginal probing (BOMP) and plaque scores (PS) in the non-brushed (lower) jaw with experimental gingivitis was significant in all groups (P < 0.001). As compared to the gum base, the increase in BOMP in the xylitol and maltitol group was significantly lower. In the brushed upper jaw, no significant changes for BOMP were observed from the baseline to the end point of the study, and there were no significant differences in BOMP and PS between the groups. CONCLUSION: In circumstances where regular brushing is performed, no effect of chewing gum was observed on bleeding and plaque scores. In the absence of brushing, chewing xylitol or maltitol gum provided a significant inhibitory effect on gingivitis scores compared to chewing gum base. The difference when compared to the group not using gum was not significant.

Effects of maltitol and xylitol chewing-gums on parameters involved in dental caries development.

AIM: The effects on plaque parameters of sugar free chewing-gums (CG) sweetened with either maltitol or xylitol were assessed to better understand the role polyols can play in dental caries prevention. MATERIALS AND METHODS: A double-blind, parallel, randomised, controlled study was conducted in China. Subjects (N = 258, age = 13 to 15 years-old) were divided into 4 groups: 2 receiving polyols CG, containing respectively maltitol or xylitol, a group receiving gum base (placebo) and a negative control group not receiving any gum. CG were chewed for 30 days. This corresponds to a 10 g consumption of polyol per day. Plaque parameters (growth, pH, bacteria and insoluble glucans) were evaluated throughout the experimental period. RESULTS: All parameters studied were significantly modified with gum base compared to no-gum: plaque pH increased; plaque growth, bacteria (S. mutans, S. sobrinus, A. viscosus and Lactobacillus) and insoluble glucans decreased. Maltitol and xylitol CG led similarly to a higher plaque pH (AUC, p⋜0.05) on short (at baseline after the first CG consumption) and long term (after 4 weeks of daily CG consumption), with or without saliva stimulation compared to both control and placebo groups. They led to a decrease in plaque growth (p=0.02) over the experimental period compared to controls. Moreover, they significantly reduced the concentration of 4 cariogenic bacteria species (p⋜0.05) in dental plaque compared to gum base. CONCLUSION: Sugar free CG sweetened with either maltitol or xylitol can similarly reduce plaque acidogenicity compared to gum base through a decrease in oral bacteria presence. The use of a gum base placebo allowed to isolate effects on parameters involved in dental caries development specific to maltitol and xylitol, and to show these effects were similar.

The caries-preventive effect of xylitol/maltitol and erythritol/maltitol lozenges: results of a double-blinded, cluster-randomized clinical trial in an area of natural fluoridation.

OBJECTIVE: Xylitol studies suggest caries reductions in the order of 50%. Based on animal/microbial studies, erythritol potentially has caries-preventive properties. However, clinical studies are required to confirm this. The aim of the study was to investigate the additional caries-preventive effect of xylitol/maltitol and erythritol/maltitol lozenges delivered at school, relative to controls receiving comprehensive prevention, in a low-caries prevalence population. METHODS: A 4-year, cluster-randomized, double-blinded clinical trial. Five hundred and seventy-nine 10-year-old consenting subjects from 21 schools were randomly assigned to one of five groups. Four groups used the lozenges on school days, in three teacher-supervised sessions daily, over 1 or 2 years. The daily amount was 4.7 g/4.6 g for xylitol/maltitol and 4.5 g/4.2 g for erythritol/maltitol. The groups received free examinations and care in the public health centre. Four hundred and ninety-six children were analysed. The main outcome measure was dentin caries increment based on a clinical examination at 4 years since the start. The groups were compared in relation to the increment using hierarchical logistic regression to adjust for potential clustering. RESULTS: Use of xylitol/maltitol or erythritol/maltitol lozenges did not result in caries reduction. A strong relationship between baseline caries prevalence and the 4-year increment was observed (OR = 7.38; 95% CI: 3.78-14.41). CONCLUSIONS: The results suggest that in relatively low-caries conditions the school-based use of xylitol/maltitol or erythritol/maltitol lozenges would not have additional caries-preventive effect when compared with comprehensive prevention.

Enzymatic Synthesis of Maltitol and Its Inhibitory Effect on the Growth of Streptococcus mutans DMST 18777.

This study aimed to synthesize maltitol using recombinant CGTase from Bacillus circulans A11 with ß-cyclodextrin (ß-CD) and sorbitol as a glucosyl donor and acceptor, respectively, and assess its antibacterial activity. Optimal conditions for producing the highest yield, 25.0% (w/w), were incubation of 1% (w/v) ß-CD and sorbitol with 400 U/mL of CGTase in 20 mM phosphate buffer at pH 6.0 and 50 °C for 72 h. Subsequently, maltitol underwent large-scale production and was purified by HPLC. By mass spectrometry, the molecular weight of the synthesized maltitol was 379.08 daltons, corresponding exactly to that of standard maltitol. The relative sweetness of synthesized and standard maltitol was ~90% of that of sucrose. Spot assay on the agar plate showed that maltitol inhibited the growth of Streptococcus mutans DMST 18777 cells. In addition, the MIC and MBC values of synthesized and standard maltitol against S. mutans were also determined as 20 and 40 mg/mL, respectively. These results show that the synthesized maltitol can be produced at high yields and has the potential to be used as an anticariogenic agent in products such as toothpaste.

A multifunctional α-amylase BSGH13 from Bacillus subtilis BS-5 possessing endoglucanase and xylanase activities.

Exploring new multifunctional enzymes and understanding the mechanisms of catalytic promiscuity will be of enormous industrial and academic values. In the present study, we reported the discovery and characterization of a multifunctional enzyme BSGH13 from Bacillus subtilis BS-5. Remarkably, BSGH13 possessed α-amylase, endoglucanase, and xylanase activities. To our knowledge, this was the first report on an amylase from Bacillus species having additional endoglucanase and xylanase activities. Subsequently, we analyzed the effects of aromatic residues substitution at each site of the active site architecture on ligand-binding affinity and catalytic specificity of BSGH13 by a combination of virtual mutation and site-directed mutagenesis approaches. Our results indicated that the introduction of aromatic amino acids Phe or Trp at the positions L182 and L183 altered the local interaction network of BSGH13 towards different substrates, thus changing the multifunctional properties of BSGH13. Moreover, we provided an expanded perspective on studies of multifunctional enzymes.

Glycyl betaine is effective in slowing down the irreversible denaturation of a detergent-solubilized membrane protein, sarcoplasmic reticulum Ca2+-ATPase (SERCA1a).

Many membrane proteins become labile when they are solubilized by detergent. Here we show that the presence of high concentrations of glycyl betaine stabilizes one of these proteins, the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA1a), solubilized with nonionic detergents like n-dodecyl beta-d-maltopyranoside (DDM) or octaethylene glycol monododecyl ether (C(12)E(8)) which are commonly used for its purification or crystallization. Betaine at high concentrations might become useful as a stabilizing agent for detergent-solubilized membrane proteins, for instance during purification procedures or during the long periods of time required for crystallogenesis.

[Preparation of orally disintegrating tablets for masking of unpleasant taste: comparison with corrective-adding methods].

Many orally disintegrating tablets have recently been developed to improve oral ingestion and usability and are widely administered clinically, resulting in improved quality of life for patients. Since orally disintegrating tablets rapidly disintegrate in the mouth, the masking of unpleasant taste is important. We investigated the masking of the taste of furosemide (FU) as a model drug with correctives and prepared orally disintegrating tablets. Using maltitol (MA) as a corrective, granules were prepared employing mixing, coating, and mixing/coating methods using a desktop granulator. Each preparation was subjected to tasting. The taste was masked well when granules were prepared by the mixing and mixing/coating methods. Tablets were prepared from these granules with mannitol and crystalline cellulose added as fillers. Tablets made from granules prepared by the mixing and mixing/coating methods showed appropriate strength and disintegrated rapidly. When the amount of MA was increased in the mixing method, the disintegration time was prolonged, and thus the amount should be determined considering both taste masking and disintegration property. The results showed that orally disintegrating tablets of insoluble drugs with an unpleasant taste such as FU should be prepared with the taste masked employing the methods used in this study.

Preparation of orally disintegrating tablets with taste-masking function: masking effect in granules prepared with correctives using the dry granulation method and evaluation of tablets prepared using the taste-masked granules.

We investigated several methods of taste masking in the preparation of orally disintegrating tablets (ODTs), using furosemide (FU) as a model drug. Four types of FU preparations were prepared: granules with maltitol (MA), granules with yogurt powder (YO), a physical mixture of FU and MA, and a physical mixture of FU and YO. All taste-masking granules were prepared using the dry granulation method. The taste of each type of preparation was evaluated. All four preparations markedly improved the taste of the FU tablets, but the mixing ratios of the correctives did not affect the masking effect. No difference in masking effect was found between MA and YO in the physical mixtures, but the masking effect in the granules with YO was superior to that of the granules with MA. Taste-masked FU tablets were prepared using the direct compression method; crystalline cellulose (Avicel PH-302) and mannitol were added as excipients at the mixing ratio of 1/1. All four types of tablets displayed sufficient hardness, but MA-containing tablets were harder than YO-containing tablets. The hardness of the tablets prepared from YO granules increased as the YO content increased. The most rapidly disintegrating tablets were those of YO granules prepared at a mixing ratio of FU/YO=1/1, which disintegrated within 20 s, followed by the tablets of MA granules prepared at a mixing ratio of FU/MA=1/1. The disintegration times of the tablets made from physical mixtures, in contrast, were longer than 200 s. Disintegration time lengthened as the mixing ratio of YO or MA increased. The hardness and disintegration time of these tablets could be controlled by varying the compression pressure. We found that YO is more useful than MA in masking unpleasant tastes and confirmed that orally disintegrating tablets with taste-masking function can be prepared using granules of YO prepared using the dry granulation method as a new corrective.

Factors influencing the solubilization of membrane proteins from Escherichia coli membranes by styrene-maleic acid copolymers.

Styrene-maleic acid (SMA) copolymers are a promising alternative to detergents for the solubilization of membrane proteins. Here we employ Escherichia coli membranes containing KcsA as a model protein to investigate the influence of different environmental conditions on SMA solubilization efficiency. We show that SMA concentration, temperature, incubation time, ionic strength, presence of divalent cations and pH all influence the amount of protein that is extracted by SMA. The observed effects are consistent with observations from lipid-only model membrane systems, with the exception of the effect of pH. Increasing pH from 7 to 9 was found to result in an increase of the solubilization yield of E. coli membranes, whereas in lipid-only model systems it decreased over the same pH range, based on optical density (OD) measurements. Similar opposite pH-dependent effects were observed in OD experiments comparing solubilization of native yeast membranes and yeast lipid-only membranes. We propose a model in which pH-dependent electrostatic interactions affect binding of the polymers to extramembraneous parts of membrane proteins, which in turn affects the availability of polymer for membrane solubilization. This model is supported by the observations that a similar pH-dependence as for SMA is observed for the anionic detergent SDS, but not for the nonionic detergent DDM and that the pH-dependence can be largely overcome by increasing the SMA concentration. The results are useful as guidelines to derive optimal conditions for solubilization of biological membranes by SMA.

Binding Hotspot and Activation Mechanism of Maltitol and Lactitol toward the Human Sweet Taste Receptor.

Human sweet taste receptor (hSTR) recognizes a wide array of sweeteners, resulting in sweet taste perception. Maltitol and lactitol have been extensively used in place of sucrose due to their capability to prevent dental caries. Herein, several molecular modeling approaches were applied to investigate the structural and energetic properties of these two polyols/hSTR complexes. Triplicate 500 ns molecular dynamics (MD) simulations and molecular mechanics/generalized Born surface area (MM/GBSA)-based free energy calculations revealed that the TAS1R2 monomer is the preferential binding site for maltitol and lactitol rather than the TAS1R3 region. Several polar residues (D142, S144, Y215, D278, E302, R383, and especially N143) were involved in polyols binding through electrostatic attractions and H-bond formations. The molecular complexation process not only induced the stable form of ligands but also stimulated the conformational adaptation of the TAS1R2 monomer to become a close-packed structure through an induced-fit mechanism. Notably, the binding affinity of the maltitol/TAS1R2 complex (ΔGbind of -17.93 ± 1.49 kcal/mol) was significantly higher than that of the lactitol/TAS1R2 system (-8.53 ± 1.78 kcal/mol), in line with the experimental relative sweetness. These findings provide an in-depth understanding of the differences in the sweetness response between maltitol and lactitol, which could be helpful to design novel polyol derivatives with higher sweet taste perception.

Effect of a Daily Dose of Snacks Containing Maltitol or Stevia rebaudiana as Sweeteners in High Caries Risk Schoolchildren. A Double-blind RCT Study.

PURPOSE: To evaluate the effect of sugar-free snacks on caries-related factors in 6- to 9-year-old schoolchildren. MATERIALS AND METHODS: Two hundred seventy-one children at risk for caries as measured through the Cariogram were randomly assigned to three groups consuming twice-daily snacks containing Stevia, maltitol or sugar for 42 days. Parents filled out a standardised questionnaire regarding personal, medical and oral behavioural information. Bleeding on probing, plaque pH and salivary mutans streptococchi (MS) and lactobacilli (LB) were assessed at baseline (t0), 42 days of snack use (t1) and 120 days after the end of use (t2). The Cariogram calculation was repeated at t1. Treatment effects were estimated using linear mixed-effects regression models. RESULTS: At t2, a decrease in cariogenic bacteria (MS X2 = 8.01, p < 0.01 and LB X2 = 4.60, p = 0.03) and an increase of the minimum pH (F = 4.48, p < 0.01), maximum pH (F = 2.88 p < 0.01) and pH drop (F = 2.95 p < 0.01) was recorded in the Stevia group compared to baseline. In the maltitol group, an improvement effect was noted: LB concentration decreased (p = 0.04) and maximum pH (F = 3.16 p < 0.01) increased. Subjects classified by the Cariogram as have a low probability of developing caries increased in the Stevia and maltitol groups (X2(4) = 25.44, p < 0.01, C*sV = 0.38 and X2(4) = 12.85, p = 0.01, C*sV = 0.27, respectively). Regression analysis underlines the effect of Stevia snacks on the cariogenic microflora, mainly on MS and plaque pH variations. CONCLUSION: The short-term administration of Stevia or maltitol snacks improves some important factors related to caries. This preventive strategy might be an additional means of combatting this common childhood disease.

Self-assembling peptide detergents stabilize isolated photosystem I on a dry surface for an extended time.

We used a class of designed peptide detergents to stabilize photosystem I (PS-I) upon extended drying under N2 on a gold-coated-Ni-NTA glass surface. PS-I is a chlorophyll-containing membrane protein complex that is the primary reducer of ferredoxin and the electron acceptor of plastocyanin. We isolated the complex from the thylakoids of spinach chloroplasts using a chemical detergent. The chlorophyll molecules associated with the PS-I complex provide an intrinsic steady-state emission spectrum between 650 and 800 nm at -196.15 degrees C that reflects the organization of the pigment-protein interactions. In the absence of detergents, a large blue shift of the fluorescence maxima from approximately 735 nm to approximately 685 nm indicates a disruption in light-harvesting subunit organization, thus revealing chlorophyll-protein interactions. The commonly used membrane protein-stabilizing detergents, N-dodecyl-beta-D-maltoside and N-octyl-beta-D-glucoside, only partially stabilized the approximately 735-nm complex with approximately 685-nm spectroscopic shift. However, prior to drying, addition of the peptide detergent acetyl-AAAAAAK at increasing concentration significantly stabilized the PS-I complex. Moreover, in the presence of acetyl-AAAAAAK, the PS-I complex is stable in a dried form at room temperature for at least 3 wk. Another peptide detergent, acetyl-VVVVVVD, also stabilized the complex but to a lesser extent. These observations suggest that the peptide detergents may effectively stabilize membrane proteins in the solid-state. These designed peptide detergents may facilitate the study of diverse types of membrane proteins.