scholarly journals High tolerance for ionizable residues in the hydrophobic interior of proteins

2008 ◽  
Vol 105 (46) ◽  
pp. 17784-17788 ◽  
Author(s):  
Daniel G. Isom ◽  
Brian R. Cannon ◽  
Carlos A. Castañeda ◽  
Aaron Robinson ◽  
Bertrand García-Moreno E.
Keyword(s):  
Water Soluble ◽  
High Tolerance ◽  
Ph Values ◽  
Internal Ionizable Groups ◽  
Ionizable Residues ◽  
Stability Dynamics ◽  
The Stability ◽  
Structural Adaptations ◽  
Ionizable Groups ◽  
Variant Protein

Internal ionizable groups are quite rare in water-soluble globular proteins. Presumably, this reflects the incompatibility between charges and the hydrophobic environment in the protein interior. Here we show that proteins can have an inherently high tolerance for internal ionizable groups. The 25 internal positions in staphylococcal nuclease were substituted one at a time with Lys, Glu, or Asp without abolishing enzymatic activity and without detectable changes in the conformation of the protein. Similar results with substitutions of 6 randomly chosen internal positions in ribonuclease H with Lys and Glu suggest that the ability of proteins to tolerate internal ionizable groups might be a property common to many proteins. Eighty-six of the 87 substitutions made were destabilizing, but in all but one case the proteins remained in the native state at neutral pH. By comparing the stability of each variant protein at two different pH values it was established that the pKa values of most of the internal ionizable groups are shifted; many of the internal ionizable groups are probably neutral at physiological pH values. These studies demonstrate that special structural adaptations are not needed for ionizable groups to exist stably in the hydrophobic interior of proteins. The studies suggest that enzymes and other proteins that use internal ionizable groups for functional purposes could have evolved through the random accumulation of mutations that introduced ionizable groups at internal positions, followed by evolutionary adaptation and optimization to modulate stability, dynamics, and other factors necessary for function.

A Novel pH-Sensitive Microsphere Composed of CM-Chitosan and Alginate for Sulforaphane Delivery

2011 ◽  
Vol 687 ◽  
pp. 539-547 ◽  
Author(s):  
Hui Wang ◽  
Hao Liang ◽  
Qi Peng Yuan ◽  
Tian Xin Wang
Keyword(s):  
Sodium Sulfate ◽  
Anticancer Agent ◽  
Ph Sensitive ◽  
Water Soluble ◽  
Ph Values ◽  
Swelling Studies ◽  
The Stability ◽  
Carboxymethylated Chitosan

Sulforaphane (SF) has been proved to be an effective anticancer agent according to its experiments bothin vitroandin vivo. To date, there is few reported method to deliver SF for increasing its bioactivity and stability. In this study, a novel pH-sensitive microsphere composed of water-soluble carboxymethylated chitosan (CMCS) and alginate mixed with sodium sulfate was developed for SF delivery. Swelling studies and release characteristics under different pH values of microspheres were investigated. Then, the release of SF from test microspheres was studied in simulated gastric and segmented intestinal media. It has been found that the SF cumulated release in 5h was increased from 55.89% to 76.73% when the microspheres mixed with sodium sulfate. In addition, the stability of SF embedded in CMCS/alginate microspheres was also significantly improved. Under pH 7.4, free SF had a severe degradation of approximate 100% within 210 min, whereas the change of the SF in microspheres was only a decrease of about 10%. The results suggested that the microspheres of CMCS and alginate could be a suitable pH-sensitive carrier to increase the stability of SF in the segmented intestine.

scholarly journals Anthocyanin Color Stabilization by Host-Guest Complexation with p-Sulfonatocalix[n]arenes

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5389
Author(s):  
Johan Mendoza ◽  
Luis Cruz ◽  
Victor de Freitas ◽  
Fernando Pina ◽  
Nuno Basílio
Keyword(s):  
Binding Pocket ◽  
Association Constants ◽  
Water Soluble ◽  
Colored Form ◽  
Cationic Form ◽  
Substitution Pattern ◽  
Ph Values ◽  
Ph Scale ◽  
The Stability ◽  
Neutral Conditions

Flavylium-based compounds in their acidic and cationic form bring color to aqueous solutions, while under slightly acidic or neutral conditions they commonly bring discoloration. Selective host-guest complexation between water-soluble p-sulfonatocalix[n]arenes (SCn) macrocycles and the flavylium cationic species can increase the stability of the colored form, expanding its domain over the pH scale. The association constants between SCn and the cationic (acid) and neutral basic forms of flavylium-based compounds were determined through UV-Vis host-guest titrations at different pH values. The affinity of the hosts for synthetic chromophore was found to be higher than for a natural anthocyanin (Oenin). The higher affinity of SC4 for the synthetic flavylium was confirmed by 1H NMR showing a preferential interaction of the flavylium phenyl ring with the host cavity. In contrast with its synthetic counterpart, the flavylium substitution pattern in the anthocyanin seems to limit the inclusion of the guest in the host’s binding pocket. In this case, the higher affinity was observed for the octamer (SC8) likely due to its larger cavity and higher number of negatively charged sulfonate groups.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

Tyrosine-Selective Bioconjugation with Iminoxyl Radicals

2020 ◽  
Author(s):  
Katsuya Maruyama ◽  
Takashi Ishiyama ◽  
Yohei Seki ◽  
Kounosuke Oisaki ◽  
Motomu Kanai
Keyword(s):  
Reaction Time ◽  
Steric Hindrance ◽  
Room Temperature ◽  
Water Soluble ◽  
Light Irradiation ◽  
Sodium Ascorbate ◽  
Iminoxyl Radical ◽  
Short Reaction Time ◽  
Modified Peptides ◽  
The Stability

A novel Tyr-selective protein bioconjugation using the water-soluble persistent iminoxyl radical is described. The conjugation proceeded with high Tyr-selectivity and short reaction time under biocompatible conditions (room temperature in buffered media under air). The stability of the conjugates was tunable depending on the steric hindrance of iminoxyl. The presence of sodium ascorbate and/or light irradiation promoted traceless deconjugation, restoring the native Tyr structure. The method is applied to the synthesis of a protein-dye conjugate and further derivatization to azobenzene-modified peptides.

BODIPY Fluorophores for Membrane Potential Imaging

2019 ◽  
Author(s):  
Jenna Franke ◽  
Benjamin Raliski ◽  
Steven Boggess ◽  
Divya Natesan ◽  
Evan Koretsky ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Water Solubility ◽  
Water Soluble ◽  
Voltage Sensitivity ◽  
Chemical Transformations ◽  
Direct Modification ◽  
Biological Compatibility ◽  
Meso Position ◽  
Ionizable Groups ◽  
Boron Center

Fluorophores based on the BODIPY scaffold are prized for their tunable excitation and emission profiles, mild syntheses, and biological compatibility. Improving the water-solubility of BODIPY dyes remains an outstanding challenge. The development of water-soluble BODIPY dyes usually involves direct modification of the BODIPY fluorophore core with ionizable groups or substitution at the boron center. While these strategies are effective for the generation of water-soluble fluorophores, they are challenging to implement when developing BODIPY-based indicators: direct modification of BODIPY core can disrupt the electronics of the dye, complicating the design of functional indicators; and substitution at the boron center often renders the resultant BODIPY incompatible with the chemical transformations required to generate fluorescent sensors. In this study, we show that BODIPYs bearing a sulfonated aromatic group at the meso position provide a general solution for water-soluble BODIPYs. We outline the route to a suite of 5 new sulfonated BODIPYs with 2,6-disubstitution patterns spanning a range of electron-donating and -withdrawing propensities. To highlight the utility of these new, sulfonated BODIPYs, we further functionalize them to access 13 new, BODIPY-based voltage-sensitive fluorophores. The most sensitive of these BODIPY VF dyes displays a 48% ΔF/F per 100 mV in mammalian cells. Two additional BODIPY VFs show good voltage sensitivity (≥24% ΔF/F) and excellent brightness in cells. These compounds can report on action potential dynamics in both mammalian neurons and human stem cell-derived cardiomyocytes. Accessing a range of substituents in the context of a water soluble BODIPY fluorophore provides opportunities to tune the electronic properties of water-soluble BODIPY dyes for functional indicators.

scholarly journals Antioxidant Network Based on Sulfonated Polyhydroxyalkanoate and Tannic Acid Derivative

2021 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Laura Brelle ◽  
Estelle Renard ◽  
Valerie Langlois
Keyword(s):  
Gallic Acid ◽  
Tannic Acid ◽  
Water Soluble ◽  
Gel Formation ◽  
Ene Reaction ◽  
Inorganic Cations ◽  
Medium Chain Length ◽  
Physically Crosslinked ◽  
The Stability ◽  
Derivatives Of

A novel generation of gels based on medium chain length poly(3-hydroxyalkanoate)s, mcl-PHAs, were developed by using ionic interactions. First, water soluble mcl-PHAs containing sulfonate groups were obtained by thiol-ene reaction in the presence of sodium-3-mercapto-1-ethanesulfonate. Anionic PHAs were physically crosslinked by divalent inorganic cations Ca2+, Ba2+, Mg2+ or by ammonium derivatives of gallic acid GA-N(CH3)3+ or tannic acid TA-N(CH3)3+. The ammonium derivatives were designed through the chemical modification of gallic acid GA or tannic acid TA with glycidyl trimethyl ammonium chloride (GTMA). The results clearly demonstrated that the formation of the networks depends on the nature of the cations. A low viscoelastic network having an elastic around 40 Pa is formed in the presence of Ca2+. Although the gel formation is not possible in the presence of GA-N(CH3)3+, the mechanical properties increased in the presence of TA-N(CH3)3+ with an elastic modulus G’ around 4200 Pa. The PHOSO3−/TA-N(CH3)3+ gels having antioxidant activity, due to the presence of tannic acid, remained stable for at least 5 months. Thus, the stability of these novel networks based on PHA encourage their use in the development of active biomaterials.

scholarly journals Measurement of the Intestinal pH in Mice under Various Conditions Reveals Alkalization Induced by Antibiotics

Antibiotics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 180
Author(s):  
Kouki Shimizu ◽  
Issei Seiki ◽  
Yoshiyuki Goto ◽  
Takeshi Murata
Keyword(s):  
Antibiotic Treatment ◽  
High Protein Diet ◽  
Intestinal Bacteria ◽  
High Protein ◽  
Protein Diet ◽  
Germ Free ◽  
Treatment Regimens ◽  
Ph Values ◽  
Specific Pathogen ◽  
The Stability

The intestinal pH can greatly influence the stability and absorption of oral drugs. Therefore, knowledge of intestinal pH is necessary to understand the conditions for drug delivery. This has previously been measured in humans and rats. However, information on intestinal pH in mice is insufficient despite these animals being used often in preclinical testing. In this study, 72 female ICR mice housed in SPF (specific pathogen-free) conditions were separated into nine groups to determine the intestinal pH under conditions that might cause pH fluctuations, including high-protein diet, ageing, proton pump inhibitor (PPI) treatment, several antibiotic treatment regimens and germ-free mice. pH was measured in samples collected from the ileum, cecum and colon, and compared to control animals. An electrode, 3 mm in diameter, enabled accurate pH measurements with a small amount of gastrointestinal content. Consequently, the pH values in the cecum and colon were increased by high-protein diet, and the pH in the ileum was decreased by PPI. Drastic alkalization was induced by antibiotics, especially in the cecum and colon. The alkalized pH values in germ-free mice suggested that the reduction in the intestinal bacteria caused by antibiotics led to alkalization. Alkalization of the intestinal pH caused by antibiotic treatment was verified in mice. We need further investigations in clinical settings to check whether the same phenomena occur in patients.

Study on Influence of Silicate Morphology Based on pH Value

2012 ◽  
Vol 454 ◽  
pp. 324-328
Author(s):  
Yan He ◽  
Ya Jing Liu ◽  
Yong Lin Cao ◽  
Li Xia Zhou
Keyword(s):  
Silicic Acid ◽  
Ph Value ◽  
Colorimetric Method ◽  
Absorption Spectrometry ◽  
Degree Of Polymerization ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ph Values ◽  
The Stability

Infra-red absorption spectrometry, X-ray diffraction observations and characterization tests based on silicon molybdenum colorimetric method were used to investigate the optimal pH value controlling the stability of the silicic acid form. The experiment process was done by using sodium silicate as raw material. The results showed that the solution of silicate influenced the polymerization. The active silicic acid solution with a certain degree of polymerization was obtained by controlling the pH values.

Development of Curcumin-Loaded Polymeric Mixed Micelle for Skin Moisturizing Antioxidant Formulation

2021 ◽  
Vol 901 ◽  
pp. 98-103
Author(s):  
Sunee Channarong ◽  
Parapat Sobharaksha ◽  
Chanchai Sardseangjun ◽  
Panipak Vasvid
Keyword(s):  
Mixed Micelle ◽  
Polymeric Micelles ◽  
Entrapment Efficiency ◽  
Water Soluble ◽  
Poloxamer 407 ◽  
Average Particle ◽  
Yellow Color ◽  
Stability Data ◽  
Hydrogenated Castor Oil ◽  
The Stability

Abstract The aim of this study was to fabricate curcumin-loaded polymeric mixed micelle which was a new nanocarrier of therpeutic agent for skin uses. Curcumin was extracted from dried turmeric rhizomes using ethanol and recrystallized. The purity of curcumin was 79±3.6 %w/w. Six curcumin-loaded polymeric micelles (PM1-PM6) were prepared by simple dissolution method using poloxamer 407 (5% and 10%) as a main core structure. PEG-40 hydrogenated castor oil (PEG-40HCO) was incorporated at two percentages (2.5% and 5.0%) to study the effect on the nanoparticle characteristics. The average particle sizes of PM1-PM6 were in the range of 33.3±6.6 nm to 171.3±52.8 nm. The entrapment efficiency and the loading capacity of curcumin were in the range of 47.45%-77.35% and 0.048%w/w-0.078%w/w, respectively. When PEG-40HCO was incorporated in to the polymeric micelles, the particle size decreased and the entrapment efficiency increased. Thus, PM4 and PM5 were selected for further study. Moisturizing antioxidant creams containing 0.005%w/w of curcumin loaded in PM4, PM5 and curcumin simply dissolved in propylene glycol (PG) were formulated. The resulted formulations showed good spreadability and good characteristics. After being subjected to accelerated test, all of the formulations remained with characteristic color, pH and showed no phase separation. The stability data showed that the moisturizing antioxidant creams were stable for the whole 3 months after storage at accelerated temperature (45°C/75%RH). The study demonstrated that polymeric mixed micelle spontaneously encapsulated a poorly water-soluble curcumin and increased the solubility up to 250 folds. The developed moisturizing cream containing 0.005%w/w of curcumin resulted a greenish-yellow color preparation. It had tolerable physicochemical properties based on curcumin content, pH and viscosity under the harsh condition. The cream also had satisfactory antioxidant activity, which can be regarded as an effective and acceptable therapeutic or skincare products for topical uses.

672 An Investigation of Antibiotic Loading and Release in Acid-precipitated Keratin Proteins to Treat Topical Burn Infections

2021 ◽  
Vol 42 (Supplement_1) ◽  
pp. S192-S193
Author(s):  
Marc A Thompson ◽  
Robert J Christy
Keyword(s):  
Proteolytic Enzymes ◽  
Diglycidyl Ether ◽  
Water Soluble ◽  
Bacterial Colony ◽  
Freeze Dried ◽  
Antibiotic Compounds ◽  
Water Ph ◽  
Stable Product ◽  
Antibiotic Release ◽  
The Stability

Abstract Introduction Human-hair derived keratin (KOS) protein has been selected in this investigation for its ability to bind antibiotic compounds and provide sustained release while withstanding harsh proteolytic environments such as inflamed, damaged tissue. The need to control local flora has been recognized as an imperative for wound healing, as recovery is significantly hampered by infection. This study investigates the synthesis of KOS-based particulate matter, developed using acid-precipitation, to load and release the water-soluble antibiotic ciprofloxacin (CIP). We hypothesize that ionically bound CIP release is tied to the degradation of KOS, therefore, bacterial metabolism, which produces proteolytic enzymes, will trigger CIP release thereby creating a novel self-extinguishing delivery system for contaminated skin wounds. Methods Ciprofloxacin hydrochloride was solubilized in deionized water (pH 5.3) under constant stirring. Freeze-dried KOS powder was added for an ultimately 5% w/v and 0.8% w/v solution of KOS and CIP, respectively. To improve the stability of KOS a water-soluble diglycidyl ether crosslinker was added to solutions and stirred for 24 hours. CIP-loaded protein was precipitated out by a hydrochloric acid induced pH reduction. Samples were collected and frozen at -20 °C prior to lyophilization, thus forming the stable product. Degradation of KOS and commensurate release of CIP were measured using a bicinchoninic acid (BCA) assay and fluorescent measurements of hydrated material supernatant. The reduction of bacterial colonies was validated by a broth inhibition assay whereby CIP-loaded KOS or unloaded KOS controls where hydrated in bacterial-laden broth cultures of Pseudomonas aeruginosa or Methicillin-resistant Staphylococcus aureus. Cultures were sampled at 24, 48, or 72 hours and plated to quantify colony-forming units. Results The presence of CIP in the KOS protein was confirmed and release rates follow similar patterns to that of KOS degradation. CIP-loaded proteins significantly reduce bacterial colony presence in concentrated inoculant solutions up to 72 hours. Conclusions CIP release does appear to coincide with KOS degradation, which is bolstered in the presence of infectious levels of bacteria. Ongoing studies aim to observe more robust models of infection and more controlled antibiotic release.

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