Acid Gel System Research Articles

Reconstruction of Postinfarcted Cardiac Functions Through Injection of Tanshinone IIA@ Reactive Oxygen Species‐Sensitive Microspheres Encapsulated in a Thermoreversible Hydrogel

Myocardial damage resulting from acute myocardial infarction often leads to progressive heart failure and sudden death, highlighting the urgent clinical need for effective therapies. Recently, tanshinone IIA has been identified as a promising therapeutic agent for myocardial infarction. However, efficient delivery remains a major issue that limits clinical translation. To address this problem, an injectable thermosensitive poly (lactic acid‐co‐glycolic acid)‐block‐poly (ethylene glycol)‐block‐poly (lactic acid‐co‐glycolic acid) gel (PLGA‐PEG‐PLGA) system encapsulating tanshinone IIA‐loaded reactive oxygen species‐sensitive microspheres (Gel−MS/tanshinone IIA) has been designed and synthesized in this study. The thermosensitive hydrogel exhibits good mechanical properties after reaching body temperature. Microspheres initially immobilized by the gel exhibit excellent reactive oxygen species‐triggered release properties in a high‐reactive oxygen species environment after myocardial infarction onset. As a result, encapsulated tanshinone IIA is effectively released into the infarcted myocardium, where it exerts local anti‐pyroptotic and anti‐inflammatory effects. Importantly, the combined advantages of this technique contribute to the mitigation of left ventricular remodeling and the restoration of cardiac function following tanshinone IIA. Therefore, this novel, precision‐guided intra‐tissue therapeutic system allows for customized local release of tanshinone IIA, presenting a promising alternative treatment strategy aimed at inducing beneficial ventricular remodeling in the post‐infarct heart.

Organic Weighting Hydraulic Fracturing Fluid: Complex Interactions between Formate Salts, Hydroxy Carboxylate Acid, and Guar

Summary Hydraulic fracturing has extended to both deep-terrestrial and deep-sea reservoirs because hydrocarbons in shallow subsurface are depleting. However, the density of common inorganic weighting agents may not give sufficient column pressure, which may compromise the efficiency of hydraulic fracturing fluids (HFF) and present potential risks to facilities and the environment. Here, we investigated hydroxypropyl guar (HPG)-based HFF (HPG-HFF) using potassium formate (PF) as a weighting agent with and without a hydroxy carboxylate acid (citric acid, abbreviation FW was used througout this study) as an additional dispersion stabilizer. Analyses included stability investigations, macro- and microrheology assessments, Fourier transform infraredspectroscopy (FTIR) analyses, molecular dynamic simulations, and screening of crosslinking points. Our results showed that increased concentrations of PF substantially reduced the stability and viscosity of HPG solutions, but adding citric acid mitigated these drawbacks. Molecular dynamic modeling suggested that formate acid ions formed hydrogen bonds with HPG and water, resulting in reduced hydrophilicity and coiling of the HPG molecular chain. When citric acid was added, less formate ions surrounded the HPG molecule, and the forming FW ions primarily interacted with the HPG molecule through hydrogen bonding. Besides, the hydroxyl group of the citric acid may improve the hydrophilicity of the whole complex. Thus, the original nature of the HPG molecular chain could be compensated. Atomic force screening showed more crosslinking points with stronger intensity and an even distribution in the HPG-PF-citric acid gel system, compared to that in the HPG-PF gel system (without citric acid). Furthermore, thermal stability tests showed that the proposed PF-citric acid-HPG-HFF system could resist temperatures up to 120°C. Our study demonstrates the potential application of formate-based weighting agents, highlighting the effects of hydrogen bonding in complex HFF. This benchtop study provides a foundation for future research to understand the application of formate-FW-based weighting HPG-HFF in downhole high temperature conditions.

Detection of enamel subsurface lesions by swept-source optical coherence tomography.

This study aimed to non-destructively analyze the progression of subsurface enamel caries using swept-source optical coherence tomography (SS-OCT), a recently developed imaging analysis modality. Artificial enamel caries at various stages of demineralization were created in bovine tooth enamel using a modified lactic acid gel system. Untreated enamel served as a control. OCT images from cross-sections of enamel were collected. Mineral density, distribution, and histological changes were analyzed using an electron probe microanalyzer, scanning electron microscopy, and contact microradiography. The Raman spectrum and X-ray structural analysis of the enamel surfaces were determined. SS-OCT detected significant differences in mineral loss among the samples. A high-brightness image was confirmed, along with changes in the respective brightness graphs proportionate to the degree of demineralization. SS-OCT can potentially be used to evaluate the progression of incipient enamel carious lesions.

Dose-Response Effects of Zinc and Fluoride on Caries Lesion Remineralization

The present mechanistic in vitro study aimed to investigate dose-response effects of zinc and fluoride on caries lesion remineralization and subsequent protection from demineralization. Artificial caries lesions were created using a methylcellulose acid gel system. Lesions were remineralized for 2 weeks using citrate-containing artificial saliva which was supplemented with zinc (0–153 µmol/l) and fluoride (1.1 or 52.6 µmol/l) in a 7 × 2 factorial design. Lesions were also remineralized in the absence of zinc and citrate, but in the presence of fluoride. After remineralization, all lesions were demineralized for 1 day under identical conditions. Changes in mineral distribution characteristics of caries lesions after remineralization and secondary demineralization were studied using transverse microradiography. At 1.1 µmol/l fluoride, zinc exhibited detrimental effects on remineralization in a dose-response manner and mainly by preventing remineralization near the lesion surface. At 52.6 µmol/l fluoride, zinc retarded remineralization only at the highest concentration tested. Zinc enhanced overall remineralization at 3.8–15.3 µmol/l. At 76.5 and less so at 153 µmol/l, zinc showed extensive remineralization of deeper parts within the lesions at the expense of remineralization near the surface. Citrate did not interfere with remineralization at 1.1 µmol/l fluoride, but enhanced remineralization at 52.6 µmol/l fluoride. Lesions exhibiting preferential remineralization in deeper parts showed higher mineral loss after secondary demineralization, suggesting the formation of more soluble mineral phases during remineralization. In summary, zinc and fluoride showed synergistic effects in enhancing lesion remineralization, however only at elevated fluoride concentrations.

The caries-reducing benefit of fluoride-release from dental restorative materials continues after fluoride-release has ended

Objective. This study tested the hypothesis that the benefit of fluoride-releasing restorative materials continues even after their reserve of fluoride has been depleted. Materials and methods. Pits in perspex blocks simulating cavities were filled with either a fluoride-releasing or a non-fluoride-releasing restorative material and a dentin single-section was placed 1 mm from the edge of the filled pit. These combinations were exposed to an acid gel system. Each demineralized dentin section was separated from the adjacent material and immersed in fresh demineralizing solutions. Transversal microradiographs were taken following the two experimental periods. This study defined ΔΔZ as the increase of integrated mineral loss (ΔZ) during the second acid attack. Results. The first acid attack substantially demineralized the near-surface region (depth < 40 μm) in all samples. The second acid attack, however, did not cause further demineralization in this near-surface region. Instead, it demineralized dentin deeper than 40–60 μm. The ΔΔZ of the material that did not release fluoride was significantly greater than that of fluoride-releasing materials. Negative correlations were found between ΔΔZ and the mineral volume% of the near-surface region and lesion body of the initial lesions. These results indicate that the dentin mineral in the near-surface region is chemically altered to become acid-resistant fluorapatite. In addition, lesion progression during the second period of demineralization, which was fluoride-free, may have been affected for the materials that have high mineral content of the surface layer and lesion body. Conclusions. It is concluded that dentin surrounding fluoride-releasing materials is protected against demineralization even after the fluoride release has diminished.

Rheological Evaluation of Polyacrylic Acid Hydrogels

A range of recently introduced polyacrylic acid gel systems (Noveon AA-1, Carbopol 974P, Carbopol EX-214) and Carbopol 934 have been examined rheologically using continuous shear, creep and oscillatory measurements. Continuous shear measurements indicated that Carbopol 934 gels have the highest viscosity, with a low degree of thixotropy, while sodium-neutralized Carbopols 974P and EX-214 gels showed differences in rheological behaviour, despite being theoretically identical in structure. Creep and oscillatory studies indicated that Carbopol 934 had the highest degree of gel network elasticity, followed by Noveon AA-1, Carbopol 974P and Carbopol EX-214.

The Effect of Fluoride at Plaque Fluid Concentrations on Enamel De- and Remineralisation at Low pH

The aim was to study the effect of fluoride, at concentrations typical of plaque fluid, on de- and remineralisation of subsurface lesions at low pH. Artificial lesions in human enamel were microradiographed to quantify mineral loss and placed in acid-gel systems at pH 4.8, 5.0 and 5.2. Calcium and phosphate were added to give initial Ca and Pi concentrations of either 4.1 and 8.0 mM, or 4.7 and 9.7 mM, at each pH value. Further, at each pH and combination of Ca and Pi, fluoride was added to the gels to give initial concentrations of 1, 2 or 5 ppm, with a non-fluoride control group. The lesions were removed after 10 days and change in mineral content quantified. Those in the non-fluoride control groups had demineralised further. Those exposed to fluoride had remineralised, the amount increasing with increasing fluoride concentration, up to a maximum value of approximately 75%. Calcium activity in the gels was reduced significantly, to levels similar to those reported for plaque fluid at low pH. Fluoride activity was also reduced, though to a lesser extent. These findings contrast with those from studies which have simulated conditions on smooth surface sites and which used experimental solutions composed to reflect salivary fluoride concentrations, where net demineralisation was observed at low pH. This reflects the need for further study of de- and remineralisation under plaque-fluid conditions. In conclusion, subsurface lesions were remineralised at low pH by fluoride at concentrations found in plaque fluid during a cariogenic challenge.

Fine defective structure of silicon carbide powders obtained from different starting materials

The fine defective structure of silicon carbide powders obtained from silicic acid-saccharose, aerosil-saccharose, aerosil-carbon black, and hydrated cellulose-silicic acid gel systems was investigated. The relation between IR absorption characteristics and the microstructure of SiC particles obtained from different starting materials was established. The numerical relationship between the lattice parameter a and the frequency ?TO is presented.

The Effect of Adjacent Dentine Blocks on the Demineralisation and Remineralisation of Enamel in vitro

The aim was to investigate interactions between enamel and dentine at low pH under conditions simulating those at the enamel-dentine junction. Sound enamel blocks were demineralised in acid-gel systems, at pH 4.6, either in isolation, next to one, or in the middle of two, abutting dentine blocks. The gels were initially infinitely undersaturated with respect to enamel. In a second study, enamel blocks containing pre-formed lesions were placed in acid-gel systems, at pH 5.0, either in isolation or next to dentine blocks. The systems were initially either partially or infinitely undersaturated. In the partially saturated systems, calcium and phosphate concentrations were representative of plaque fluid. In the first study, demineralisation of enamel next to one dentine block was reduced in inverse proportion to the distance from the dentine. Demineralisation of enamel between two dentine blocks was retarded markedly across the whole block. In the second study, in the partially saturated systems, enamel lesions next to dentine blocks remineralised, whereas those in isolation demineralised further. We suggest that diffusion of dissolved dentine mineral over the enamel in the infinitely undersaturated system was sufficient to reduce undersaturation, thus retarding demineralisation, and that in the partially saturated systems, dentine dissolution together with the added calcium phosphate caused remineralisation of enamel lesions. Fluoride released from dissolving dentine may have augmented these effects. Different rates of demineralisation in enamel and dentine, or enamel remineralisation with concurrent dentine demineralisation, enabled by differences in their solubilities, could help explain the progression of so-called ‘hidden caries’.

Development of an in situ root caries model. A. In vitro investigations

The paper describes preliminary in vitro investigations, the objectives of which were to examine the influence of certain experimental parameters on artificial carious lesion formation in root hard tissues, and their remineralisation. These experiments formed part of a wider study that aimed to develop an in situ model of root caries, based on the existing coronal caries model used in Liverpool. The present studies examined the effects (a) of the anatomical origin of the dentine, the presence or absence of cementum, the exposure time and the type of demineralising system, on lesion development, and (b) of baseline lesion size on the extent and location of mineral re-precipitation. Mineral content parameters in plano-parallel sections taken from dentine lesions were determined by computer-controlled transverse microradiography. The importance of the anatomical origin of the dentine on lesion formation was investigated by comparing in vitro lesion formation in premolar and molar dentine, and in dentine from apical, middle and coronal thirds of the root: no difference was observed between these sites. Lesions formed more rapidly in acid buffer solutions than in acid gel systems, and were more reliably produced when cementum was removed. The effect of baseline lesion size on subsequent in vitro remineralisation demonstrated that a small baseline mineral content was associated with a larger percentage mineral gain. The location of mineral deposition throughout the lesion was also influenced by baseline mineral content parameters. The results form a basis for the further development of an in situ dentinal caries model, providing data to suggest that manipulation of parameters involved in the preparation of artificial carious lesions has a significant effect on the behaviour of the lesion, particularly the phenomenon of remineralisation. Further work is needed to investigate the behaviour of the model in situ.

Resin Tag Length of One-Step and Self-Etching Adhesives Bonded to Unground Enamel

Length of resin tags yielded by utilization of an one-step conventional adhesive system and self-etching adhesive system on unground enamel was observed. In study Groups I and III, the enamel surface was etched for 60 seconds with 35% phosphoric acid gel and adhesive systems PQ1 (Ultradent Products, Inc) and Adper Prompt L Pop (3M/ESPE) were applied. Adper Prompt L Pop (3M/ESPE) was also applied in Group II in accordance with the manufacturer's recommendations. After application of these adhesive systems to dental enamel, specimens were prepared for light microscopy analysis to ascertain degree of penetration (x400). The results were submitted to an analysis of variance at the 5% level; whenever there was significance, the Tukey test was applied at the 5% level. It was found that acid etching prior to application of conventional and self-etching adhesive materials provided higher penetration of the adhesive into the unground enamel surface compared to that achieved solely by application of self-etching adhesive.

Light-Induced Fluorescence Studies on Dehydration of Incipient Enamel Lesions

Changes in the hydration state of enamel affect its optical qualities, such as light scattering and fluorescence. In this study, the rate of fluorescence loss was measured when incipient enamel lesions with different de-remineralization history were left to dehydrate. Four groups of lesions were studied. In groups A, B and C, the lesions were prepared in vitro in an acid-gel system. Group A was kept as control, and groups B and C were remineralized (4 weeks) without and with 1 ppm F in solution, respectively. Group D consisted of natural incipient lesions. Enamel fluorescence was measured for all lesions immediately after removal from water and subsequently at short intervals for 30 min. The change in fluorescence with dehydration varied between the groups. In lesions from groups A and B, it followed a double exponential decrease, while in lesions from groups C and D, it followed a mono-exponential decrease. In all groups, the fluorescence of sound surfaces declined mono-exponentially. The ‘fractional fluorescence difference’, defined as (L_sound – L_carious )/L_sound, became constant after periods of dehydration of about 5, 5, 20 and 5 min for groups A to D, respectively. The observation of the change of fluorescence with dehydration should be taken into consideration when planning studies that use fluorescence as an assessment method. However, it might also be used to gain insight into the properties for fluid transport inside the various lesions, relevant to de-remineralization or fluoride treatments.

Formation and Physical Properties of Milk Protein Gels

Gelation of milk proteins is the crucial first step in both cheese and yogurt manufacture. Several types of milk gels are discussed, with an emphasis on recent developments in our understanding of how these gels are formed and some of their key physical properties. Areas discussed include the latest dual-binding model for casein micelles; some recent developments in rennet-induced gelation; review of the methods that have been used to monitor milk coagulation; and a discussion of some of the possible causes for the wheying-off defect in yogurts. Casein micelles are the primary building blocks of casein-based gels; however, controversy about its structure continues. The latest model proposed for the formation of casein micelles is the dual-binding model proposed by Horne, 1998, which suggests that casein micelles are formed as a result of two binding mechanisms, namely hydrophobic attraction and colloidal calcium phosphate (CCP) bridging. Most previous models for the casein micelle have treated milk gelation from the viewpoint of simple particle destabilization and aggregation, but they have not been able to explain several unusual rheological properties of milk gels. Although there have been many techniques used to monitor the milk gelation process over the past few decades, only a few appear attractive as possible in-vat coagulation sensors. Another important aspect of milk gels is the defect in yogurts called wheying-off, which is the appearance of whey on the gel surface. The factors responsible for its occurrence are still unclear, but they have been investigated in model acid gel systems.

Effects of starter culture and its exopolysaccharides on the gelation of glucono‐δ‐lactone‐acidified bovine and caprine milk

The effects of the starter culture biomass material and its exopolysaccharides (EPS) on the structure of bovine and caprine acid gels were investigated. Inactivated cell material and/or extracellular polysaccharide, which had been separated from yogurt starter cultures, were added to both types of milk. The milk systems were acidified using glucono‐δ‐lactone (GDL) and the gelation processes were monitored using dynamic (oscillatory) rheological testing. The addition of cell material had no effect on the bovine acid gel, whereas the addition of polysaccharide produced a weaker gel structure. The addition of cell material (&gt; 5 × 108 cells/mL) and polysaccharide (0.35% w/v) weakened the caprine acid gel system. The treated gels were some three to eight times weaker than the untreated samples, suggesting that the starter culture metabolites and especially the EPS may act by interfering with the gel structures, particularly in the cases of milk systems such as caprine yogurt or low protein content bovine yogurt.

Fluoride Uptake to Demineralised Enamel: A Comparison of Sampling Techniques

Fluoride uptake is a recognised way of assessing the potential anticaries efficacy of fluoride (F) treatments. The aim of the present study was to compare an abrasion method of sampling treated enamel, based on that of Weatherell et al. [Caries Res 1985;19:97–102], with the acid–etch method of Raven et al. [Caries Res 1991;25:130–137]. Two adjacent demineralised areas were created on the polished surfaces of bovine incisors using an acid gel system. One artificial lesion from each tooth was subsequently treated for 6 h at 37°C with one of two fluoridated dentifrice slurries (1 part: 3 parts water), whereas the other was treated similarly with a slurry of non–F control dentifrice. One set of treated lesions was then separated, the base of each enamel block polished until planoparallel with the demineralised surface and the lesions isolated by cutting away the adjacent sound enamel. Each block was mounted on the probe of a digital micrometer and the demineralised surface abraded with silicon carbide lapping film until sound material was reached. Abraded material was dissolved in perchloric acid and the buffered solution analysed for fluoride by ion–selective electrode. Each lesion of a second set of treated, demineralised enamel blocks was etched by 20μl acid and the resulting solutions analysed for F. Mean F uptakes [μg cm^–2 (SD)] were: abrasion (n = 7/treatment); F dentifrice A = 1.39 (0.89) and B = 0.86 (0.45) relative to non–F controls = 0.11 (0.12), 0.14 (0.06), respectively; and acid–etch (n = 14/treatment); A = 1.27 (0.49), B = 0.69 (0.23), controls = 0.12 (0.06), 0.12 (0.06), respectively. Significant differences (p<0.05) for both data sets were: A>B> control. The results show good agreement between the sampling methods and demonstrate the ability of the abrasion technique to distinguish between F treatments.

The effects of ageing on the rheological, dielectric and mucoadhesive properties of poly(acrylic acid) gel systems.

The purpose of this study was to investigate the effects of storage on the physical properties of a series of poly(acrylic acid) (PAA) hydrogels, using two dynamic techniques, oscillatory rheology and dielectric spectroscopy. Furthermore, the effects of ageing on the mucoadhesive properties were evaluated and related to the changes in structure. Three carbomers (Carbopols 934P, 974P and EX-214) and polycarbophil (Noveon AA-1) have been formulated as hydrogels with a range of neutralising agents (NaOH, triethanolamine and tromethamine). The effects of storage for six months on the gel structure were measured using oscillatory rheology and low frequency dielectric analysis. Mucoadhesive performance was studied by means of a detachment force test. A substantial decrease in the rheological storage moduli was noted for all samples, while the tan delta values remained unchanged for the majority of systems. Dielectric studies revealed that gels neutralised with triethanolamine showed a greater degree of binding of neutralising ions to the gel network than did the other two agents. It was also found by the dielectric analysis that, on storage, the distribution of ions within the gel systems changed. This may be due to the neutralising ions being liberated from the gel network into the bulk aqueous phase, thereby contributing to the decrease in rheological storage modulus. Mucoadhesion studies indicated that, despite the substantial changes in gel structure, there was no alteration in the bioadhesive force of detachment for the majority of systems during a six month period. A redistribution of cations between the polymer cluster and the bulk of medium is proposed as a possible additional mechanism of ageing of PAA hydrogels. The results obtained support the hypothesis outlined previously that the mucoadhesive strength is related to the tan delta value rather than the viscosity of the gel.

An investigation into the rheological, dielectric and mucoadhesive properties of poly(acrylic acid) gel systems

A range of recently introduced poly(acrylic acid) polymers (Carbopols 974P, 934P and EX-214, Noveon AA-1) have been prepared as 2.5% w/w gels in water using three different neutralising agents: sodium hydroxide, triethanolamine (TEA) and tromethamine (Tris). The structures of the gels were characterised in comparison to unneutralised systems using oscillatory rheology and low frequency dielectric spectroscopy. Rheological evaluation indicated that the elastic moduli of the gels decreased in the rank order Carbopol 934P, 974P, Noveon AA-1 and Carbopol EX-214, with the reverse order being observed for the tan δ values. The effects of changing the neutralising agent were less marked. The dielectric responses showed differences between the various polymers and also between the same polymer with different neutralising agents. In particular, samples neutralised with TEA consistently showed a greater low frequency conductance than gels neutralised with the other agents. This effect was associated with charges being more closely bound into the polymer network in the TEA neutralised gels. It was also noted that the rheological and dielectric behaviour of NaOH neutralised Carbopol 974P was markedly different to that of Carbopol EX-214, despite the supposed equivalence of these two materials. The mucoadhesive properties of the various gels were compared using a force of detachment test. It was shown that Carbopols 934P and 974P showed the greatest mucoadhesive strength, with smaller differences being noted between systems containing the various neutralising agents. A correlation between mucoadhesive strength and rheological tan δ values was observed.

Structure of Artificial Enamel Lesions after Topical Applications of High-Concentration Sodium Fluoride Solution in vitro

A three-layer structure, including a columnar layer (CL), a buffer layer, and unaffected intact enamel, was successively formed from the outer to the inner part of artificial enamel lesions (AEL) by topical applications of a high-concentration acidic sodium fluoride solution (10,000 ppm, pH 5.6) in vitro. The AEL was produced in bovine enamel that was decalcified for 5 days in a lactic acid gel system. The morphological observations by using scanning electron microscopy showed that the CL was made of columnar deposits of small globules about 0.5 microns in diameter. It was observed for the first time that small globules filled the demineralized interprismatic regions in the buffer layer. The unaffected intact enamel was protected from further demineralization under the acidic condition. Structure and composition of the CL were investigated by using X-ray diffraction and X-ray photoelectron spectroscopy. In the CL the atomic ratio was Ca:P = 12.6 and Ca:F = 0.75, and the small globules were mainly a mixture of polycrystalline calcium fluoride and hydroxyapatite. For comparison, the sound enamel and the AEL attained by applications of 0 and 100 ppm acidic sodium fluoride solutions (pH 5.6) were also investigated. The formation mechanism of the three-layer structure and the related cariostatic effects are discussed.

Coagulation Proteins in the Seminal Vesicle and Coagulating Gland of the Mouse1

As part of a program to study the formation of the vaginal plug in the mouse, we estimated the number of proteins taking part in the coagulation process, using two electrophoretic methods. Acid polyacrylamide disc gel electrophoresis (pH 4.3) gave 11 basic seminal vesicle protein bands, of which 7 disappeared from the supernatant following coagulation in vitro. Polyacrylamide gel isofocusing on the other hand gave a pattern of 25 protein bands, of which 5 disappeared from the supernatant following coagulation in vitro. The 5 bands focused within the pH range 8.2 to 9.3 and corresponded to the 7 bands removed by coagulation in the acid gel system. The data thus suggest that as many as 5, and perhaps 7, soluble proteins may take part in coagulation. The principal band in both systems focused in the pH 9.3 region and had a molecular weight of 43,000 estimated by SDS gel electrophoresis. We found no genetic variation in electrophoretic pattern of basic fraction proteins among mice of the 16 inbred strains and three translocation stocks examined. Acid gel electrophoresis of rat seminal vesicle gland (SVG) secretion, before and after coagulation in vitro, gave patterns similar to those of the mouse. Seven of eleven bands having Rf values like those of the mouse disappeared following in vitro coagulation. Rat and mouse heterologous coagulating gland-seminal vesicle gland (CG-SVG) coagulation mixtures gave similar patterns.

Membranes of chromaffin granules. Isolation and partial characterization of two proteins

Membranes of chromaffin granules were isolated from the adrenal glands of four different species. The solubilized membrane proteins could be resolved into several bands by polyacrylamide-gel electrophoresis (alkaline and acid gel systems). Two major protein components appeared to be common to the chromaffin granule membranes of ox, horse, pig and man. The various membrane proteins of bovine chromaffin granules were separated by filtration on Sephadex G-200 in the presence of sodium dodecyl sulphate. Two major membrane proteins (A and B) were obtained in purified form. Treatment of protein A with 2-mercaptoethanol before electrophoresis resulted in two more rapidly migrating subunits, whereas protein B was unaffected by mercaptoethanol treatment. The amino acid compositions of the two purified proteins were determined. They are very similar to that of the total membrane proteins but significantly different from that of the chromogranins, the soluble proteins of chromaffin granules.