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- ArticleWang F, Zhang X, Fu R, Sun G.RSC Adv. 2018 Aug 20;8(52):29745-29755.This study describes the detection of driving fatigue using the characteristics of brain networks in a real driving environment. First, the θ, β and 36-44 Hz rhythm from the EEG signals of drivers were extracted using wavelet packet decomposition (WPD). The correlation between EEG channels was calculated using a Pearson correlation coefficient and subsequently, the brain networks were built. Furthermore, the clustering coefficient (C) and global efficiency (G) of the complex brain networks were calculated to analyze the functional differences in the brains of drivers over time. Combined with the relative power spectrum ratio (β/θ) of EEG signals and the mean value from questionnaires, the correlation of data characteristics between brain networks and subjective and objective data was analyzed. The results show that changes in the fatigue state of drivers can be effectively detected by calculating the data characteristics of brain networks in a real driving environment.
- ArticleLi J.Environ Sci Pollut Res Int. 2022 Apr;29(20):29735-29745.A comprehensive understanding of the multiple factors affecting ecosystem services (ESs) supply and demand balance is essential for effective ecosystem management and policy making. However, the importance of individual factors for ES balance is still unclear. Using Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) models and Structural Equation Modeling, I mapped the supply-demand balance of four types of ESs (carbon sequestration, water yield, soil conservation, and recreation) in Taihu Lake Basin, China, and quantified the causal relationships between multiple factors and ES balance. The results revealed spatial heterogeneity and imbalance in ES supply and demand in the basin, with the greatest imbalances in built-up city center areas. ES balance was influenced by multiple factors, but particularly normalized difference vegetation index (NDVI), elevation, precipitation, and human disturbance. For appropriate watershed management in the future, it is recommended that numbers of small-scale community parks in city centers be increased and that green space be expanded in the suburbs, implementing multi-objective ES management systems and step-by-step implementation plans, and optimizing the configuration of natural ecosystems by creating buffer strips for built-up areas. By carefully managing ES supply-demand balance and associated influencing factors, ecosystem status and human well-being in Taihu Lake Basin, and in other similar basins, can be substantially improved.
- ArticleAmaral Silva D, Löbenberg R, Davies NM.J Pharm Pharm Sci. 2018;21(1s):29745.PURPOSE: The U.S. Pharmacopeia defines excipients as substances other than the active pharmaceutic ingredient (API) that are added in a drug delivery system in order to aid in the manufacturing process and enhance stability, bioavailability, safety, effectiveness and delivery of the drug. The 1968 phenytoin intoxication outbreak in Brisbane, Australia, is a classic example of an API-excipient interaction. When administered with CaSO4 the absorption of phenytoin was reduced due to an interaction between the API and the excipient. When CaSO4 was replaced by lactose, the amount of drug absorbed was much higher, resulting in the observed intoxication. It was hypothesized that phenytoin was converted to a calcium salt prior to ingestion. The purpose of this study was to mechanistically investigate the interactions between excipients and phenytoin to confirm the hypothesis of the previous reports.
METHODS: Titration experiments with phenytoin and calcium salt were performed. Isothermal micro calorimetry was used to determine incompatibilities between excipients, phenytoin and milk. NMR was used to characterize the compounds. Dissolution tests containing CaSO4, lactose or sorbitol as excipients were also performed. Both Canadian and United States of America commercially available capsules were tested with milk and water.
RESULTS: The calorimeter results indicate that phenytoin sodium interacts with CaSO4 in aqueous media and the dissolution profile of CaSO4 containing capsules showed a reduced dissolution rate. In addition, phenytoin sodium also interacts with lactose through a Maillard reaction that can occur at body temperature. Likewise, commercial Phenytoin sodium products interacted with milk and the products containing lactose showed browning in water.
CONCLUSION: In Canada and the USA, the reference product contains lactose as an excipient in the formulation, whereas the Canadian generic formulations do not contain lactose. Any clinical relevance of these difference has not been determined. A new incompatibility between phenytoin and lactose has been discovered and an incompatibility with calcium was confirmed, which may have implications in regard to excipients and food effects. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page. - ArticleChen L, Cao C, Lai H, Zhu Y, Pu M, Zheng N, He F.ACS Appl Mater Interfaces. 2021 Jun 30;13(25):29737-29745.The development of isomeric molecules has been widely exploited in molecular structures associated with organic solar cells (OSC) and is an effective pathway to finely tune the photoelectric properties and device performance. The molecular properties of nonfullerene acceptors and the morphology of blend films can be effectively controlled by manipulating isomeric substituent positions on benzene-fused end-capping groups (EG) in acceptors. Here, three isomeric EGs were designed and synthesized which simultaneously possess an electron-withdrawing bromine and an electron-donating methyl substituent. By linking three isomeric EGs, (Br,Me), (Br,Me)-1, and (Br,Me)-2 each with the BTP-CHO core, three isomeric small-molecule acceptors (SMA) were obtained. The power conversion efficiency (PCE) of PM6:BTP-(Br,Me)-1-based OSCs is 13.43%, is much higher than that of PM6:BTP-(Br,Me)- (11.92%) and PM6:BTP-(Br,Me)-2- (11.08%) based devices. Our results show that isomeric EGs can provide strategies to tune the absorption spectra of SMAs, intramolecular charge transfer (ICT) and electron mobility of organic semiconductor device, and ultimately increase the performance of nonfullerene acceptors.
- ArticleShao P, Ding L, Luo J, Luo Y, You D, Zhang Q, Luo X.ACS Appl Mater Interfaces. 2019 Aug 21;11(33):29736-29745.Zirconium oxide (ZrO2) nanoadsorbents exhibit great potential in the remediation of arsenic-polluted water. However, physicochemical structure-adsorption performance relationship is not well-understood, which retards further development of high-performance ZrO2 nanoadsorbents. Herein, a facile-controlled crystallization strategy was developed to synthesize defective ZrO2 with the assistance of organic ligands. Systematic characterizations showed that this proposed synthesis strategy can be exploited to regulate the defective density of ZrO2, whereas other structural properties remain almost unchanged. Batch adsorption experiments exhibited that UiO-66-SH-A with a higher lattice defect possessed a larger capacity and a faster rate for the uptake of As(III)/As(V). The maximum capacities of UiO-66-SH-A to uptake As(III) and As(V) were up to 90.7 and 98.8 mg/g, respectively, which are 12.3 and 11.5 times larger than those of UiO-66-A. These results from the structure-performance analysis and theoretical calculations further reveal that lattice defect plays a key role in the enhancement of arsenic adsorption on ZrO2. We hope this new understanding of the structure-dependent adsorption performance will provide a valuable insight for designing Zr-based nanoadsorbents to capture arsenic.
- ArticleLi X, Fang H, Weng X, Zhang L, Dou X, Yang A, Yuan X.Opt Express. 2015 Nov 16;23(23):29738-45.The hydrodynamic theory is a powerful tool to study the nonlocal effects in metallic nanostructures that are too small to obey classical electrodynamics while still too large to be handled with a full quantum-mechanical theory. The existing hydrodynamic model can give accurate quantitative predictions for the plasmonic resonance shifts in metallic nanoplasmonics, yet is not able to predict the spectral width which is usually taken as a pre-set value instead. By taking account the fact that due to electron density spill-out from a surface, the Coulomb interaction screening is less efficient close the surface thus leads to a higher electron-electron scattering rate in this paper, we study how the electron-density-related damping rate induced by such Coulomb interaction will affect the plasmonic spectral broadening. We perform the simulation on a Na nanowire, which shows that the absorption spectra width is wider when the size of the nanowire becomes smaller. This result is consistent well with the reported experiment. Therefore, our theoretical model extends the existing hydrodynamic model and can provide much more quantum insight about nonlocal effects in metallic nanostructures.
- Bookedited by the WHO Classification of Tumours Editorial Board.Contents:
List of abbreviations
Foreword
TNM staging of carcinomas of the breast
Introduction to tumours of the breast
Epithelial tumours of the breast
Fibroepithelial tumours and hamartomas of the breast
Tumours of the nipple
Mesenchymal tumours of the breast
Haematolymphoid tumours of the breast
Tumours of the male breast
Metastases to the breast
Genetic tumour syndromes of the breast
Contributors
Declaration of interests
IARC/WHO Committee for ICD-O
Sources
References
Subject index
Previous volumes in the series - ArticleLiang X, Kumar S.Opt Express. 2014 Dec 01;22(24):29733-45.A recursive perturbation theory to model the fiber-optic system is developed. Using this perturbation theory, a multi-stage compensation technique to mitigate the intra-channel nonlinear impairments is investigated. The technique is validated by numerical simulations of a single-polarization single-channel fiber-optic system operating at 28 Gbaud, 32-quadrature amplitude modulation (32-QAM), and 40 × 80 km transmission distance. It is found that, with 2 samples per symbol, the multi-stage scheme with eight compensation stages increases the Q-factor as compared with linear compensation by 4.5 dB; as compared with single-stage compensation, the computational complexity is reduced by a factor of 1.3 and the required memory for storing perturbation coefficients is decreased by a factor of 13.
- ArticleReschke S, Sigfridsson KG, Kaufmann P, Leidel N, Horn S, Gast K, Schulzke C, Haumann M, Leimkühler S.J Biol Chem. 2013 Oct 11;288(41):29736-45.The molybdenum cofactor is an important cofactor, and its biosynthesis is essential for many organisms, including humans. Its basic form comprises a single molybdopterin (MPT) unit, which binds a molybdenum ion bearing three oxygen ligands via a dithiolene function, thus forming Mo-MPT. In bacteria, this form is modified to form the bis-MPT guanine dinucleotide cofactor with two MPT units coordinated at one molybdenum atom, which additionally contains GMPs bound to the terminal phosphate group of the MPTs (bis-MGD). The MobA protein catalyzes the nucleotide addition to MPT, but the mechanism of the biosynthesis of the bis-MGD cofactor has remained enigmatic. We have established an in vitro system for studying bis-MGD assembly using purified compounds. Quantification of the MPT/molybdenum and molybdenum/phosphorus ratios, time-dependent assays for MPT and MGD detection, and determination of the numbers and lengths of Mo-S and Mo-O bonds by X-ray absorption spectroscopy enabled identification of a novel bis-Mo-MPT intermediate on MobA prior to nucleotide attachment. The addition of Mg-GTP to MobA loaded with bis-Mo-MPT resulted in formation and release of the final bis-MGD product. This cofactor was fully functional and reconstituted the catalytic activity of apo-TMAO reductase (TorA). We propose a reaction sequence for bis-MGD formation, which involves 1) the formation of bis-Mo-MPT, 2) the addition of two GMP units to form bis-MGD on MobA, and 3) the release and transfer of the mature cofactor to the target protein TorA, in a reaction that is supported by the specific chaperone TorD, resulting in an active molybdoenzyme.
- ArticleDoroudgar S, Thuerauf DJ, Marcinko MC, Belmont PJ, Glembotski CC.J Biol Chem. 2009 Oct 23;284(43):29735-45.Stresses that perturb the folding of nascent endoplasmic reticulum (ER) proteins activate the ER stress response. Upon ER stress, ER-associated ATF6 is cleaved; the resulting active cytosolic fragment of ATF6 translocates to the nucleus, binds to ER stress response elements (ERSEs), and induces genes, including the ER-targeted chaperone, GRP78. Recent studies showed that nutrient and oxygen starvation during tissue ischemia induce certain ER stress response genes, including GRP78; however, the role of ATF6 in mediating this induction has not been examined. In the current study, simulating ischemia (sI) in a primary cardiac myocyte model system caused a reduction in the level of ER-associated ATF6 with a coordinate increase of ATF6 in nuclear fractions. An ERSE in the GRP78 gene not previously shown to be required for induction by other ER stresses was found to bind ATF6 and to be critical for maximal ischemia-mediated GRP78 promoter induction. Activation of ATF6 and the GRP78 promoter, as well as grp78 mRNA accumulation during sI, were reversed upon simulated reperfusion (sI/R). Moreover, dominant-negative ATF6, or ATF6-targeted miRNA blocked sI-mediated grp78 induction, and the latter increased cardiac myocyte death upon simulated reperfusion, demonstrating critical roles for endogenous ATF6 in ischemia-mediated ER stress activation and cell survival. This is the first study to show that ATF6 is activated by ischemia but inactivated upon reperfusion, suggesting that it may play a role in the induction of ER stress response genes during ischemia that could have a preconditioning effect on cell survival during reperfusion.
- ArticleZhou JQ, Tan CK, So AG, Downey KM.J Biol Chem. 1996 Nov 22;271(47):29740-5.The catalytic subunit of human DNA polymerase delta has been overexpressed in insect cells by a recombinant baculovirus. The recombinant protein has a Mr = approximately 125,000 and is recognized by polyclonal antisera against N-terminal and C-terminal peptides of the catalytic subunit of human DNA polymerase delta. The recombinant protein was purified to near homogeneity (approximately 1200-fold) from insect cells by chromatography on DEAE-cellulose, phosphocellulose, heparin-agarose, and single-stranded DNA-cellulose. The purified protein had both DNA polymerase and 3'-5' exonuclease activities. The properties of the recombinant catalytic subunit were compared with those of the native heterodimeric DNA polymerase delta isolated from fetal calf thymus, and the enzymes were found to differ in several respects. Although the native heterodimer is equally active with either Mn2+ or Mg2+ as divalent cation activator, the recombinant catalytic subunit is approximately 5-fold more active in Mn2+ than in Mg2+. The most striking difference between the two proteins is the response to the proliferating cell nuclear antigen (PCNA). The activity and processivity of native DNA polymerase delta are markedly stimulated by PCNA whereas it has no effect on the recombinant catalytic subunit. These results suggest that the small subunit of DNA polymerase delta is essential for functional interaction with PCNA.
- ArticleStapleton G, Steel M, Richardson M, Mason JO, Rose KA, Morris RG, Lathe R.J Biol Chem. 1995 Dec 15;270(50):29739-45.hct-1 (hippocampal transcript) was detected in a differential screen of a rat hippocampal cDNA library. Expression of hct-1 was enriched in the formation but was also detected in rat liver and kidney, though at much lower levels; expression was barely detectable in testis, ovary, and adrenal. In liver, unlike brain, expression was sexually dimorphic; hepatic expression was greatly reduced in female rats. In mouse, brain expression was widespread, with the highest levels being detected in corpus callosum; only low levels were detected in liver. Sequence analysis of rat and mouse hct-1 cDNAs revealed extensive homologies with cytochrome P450s (CYPs), a diverse family of heme-binding monooxygenases that metabolize a range of substrates including steroids, fatty acids, and xenobiotics. Among the CYPs, hct-1 is most similar (39% at the amino acid sequence) to cholesterol 7 alpha-hydroxylase (CYP7) and contains a postulated steroidogenic domain present in other steroid-metabolizing CYPs but clearly represents a type of CYP not previously reported. Genomic Southern analysis suggests that a single gene corresponding to hct-1 is present in mouse, rat, and human. hct-1 is unusual in that, unlike all other CYPs described, the primary site of expression is in the brain. Similarity to CYP7 and other steroid-metabolizing CYPs may argue that hct-1 (CYP7B) plays a role in steroid metabolism in brain, notable because of the documented ability of brain-derived steroids (neurosteroids) to modulate cognitive function in vivo.
- ArticleJung JE, Karoor V, Sandbaken MG, Lee BJ, Ohama T, Gesteland RF, Atkins JF, Mullenbach GT, Hill KE, Wahba AJ.J Biol Chem. 1994 Nov 25;269(47):29739-45.The UGA selenocysteine (Sec) codon in glutathione peroxidase mRNA and in selenoprotein P and the UGA stop codon in rabbit beta-globin mRNA were employed to study the utilization of Sec-tRNA[Ser]Sec and Ser-tRNA[Ser]Sec in protein synthesis. In vitro Ser-tRNA[Ser]Sec served as a suppressor of the UGA Sec codon as well as the UGA stop codon, while Sec-tRNA[Ser]Sec did not. However, in vivo Sec-tRNA[Ser]Sec did donate Sec to glutathione peroxidase in Xenopus oocytes microinjected with glutathione peroxidase mRNA and Sec-tRNA. A ribosome binding assay was devised to investigate the interaction of aminoacyl-tRNA, rabbit reticulocyte ribosomes, and eukaryotic elongation factor 1 (eEF-1) in response to the appropriate trinucleoside diphosphate template. Ser-tRNA[Ser]Sec bound weakly to ribosomes in the presence of eEF-1 and UGA as compared to Phe-tRNA, Ser-tRNAIGA, and Met-tRNAm which bound more efficiently in the presence of eEF-1 and the appropriate template. No increase in the binding of Sec-tRNA[Ser]Sec was observed under the same conditions as Ser-tRNA[Ser]Sec. The ribosome binding studies substantiated the finding that Ser-tRNA[Ser]Sec serves as a suppressor of UGA codons in protein synthesis, but Sec-tRNA[Ser]Sec does not. In addition, these studies provide strong evidence that a specific elongation factor is required in mammalian cells for insertion of Sec into protein from Sec-tRNA[Ser]Sec.
- ArticleHeckler TG, Day RA.Biochim Biophys Acta. 1983 Jun 29;745(3):292-300.Penicillinase from Bacillus cereus 569/H was purified to homogeneity. Its active site was probed by use of an affinity label generated in situ by the diazotization of 6-aminopenicillanic acid, a catalytically poor substrate for this enzyme. The loss of activity arising during the inactivation is dependent upon pH and the penicillin:sodium nitrite ratio used. Optimal inactivation was obtained at pH 4.7 and reactivation could be prevented if subsequent purification and manipulations were performed at low pH. Inactivation by diazotized 6-aminopenicillanic acid was characterized further by tryptic and chymotryptic digestion of the inactivated enzyme and peptide mapping of the resulting digests. Amino acid analysis of the chymotryptic labeled peptide yielded a composition which corresponds to residues 41-46 (Ala-Phe-Ala-Ser-Thr-Tyr) in the published partial sequence of the enzyme (Thatcher, D. (1975) Biochem. J. 147, 313-326). Further digestion of this chymotryptic peptide with carboxypeptidase A reveals that serine-44 is modified in this affinity labeling procedure. Mass spectral analysis of the modified serine residue and alkali-released label, and comparison with spectra of model compounds indicates that the inactivation occurs with rearrangement of the beta-lactamthiazolidine structure to a dihydrothiazine.
- ArticleRavi A, Balaram P.Biochim Biophys Acta. 1983 Jun 29;745(3):301-9.A synthetic model peptide, (formula; see text) which mimics the active-site disulfide loop of thioredoxin has been prepared. 270 MHz 1H-NMR studies establish that Cys-4 and methylamide NH groups are solvent-shielded, using hydrogen-deuterium exchange, solvent and temperature dependence of chemical shifts and nitroxide radical-induced broadening as diagnostic criteria. Infrared measurements provide supporting evidence for intramolecularly hydrogen-bonded conformations. The related peptide in which Gly-2 is replaced by alpha-aminoisobutyric acid has been shown to adopt a similar backbone conformation based on NMR and CD data. Based on the known stereochemical preferences of alpha-aminoisobutyric acid residues, a consecutive beta-turn conformation involving two intramolecular 4 leads to 1 hydrogen bonds is proposed for both disulfides. Vicinal coupling constants and CD data are discussed with reference to the side-chain conformation of the cysteine residues. Large structural differences have been established between the thioredoxin active-site model disulfide and its acyclic precursor.
- ArticleMawatari K, Matsukawa S, Yoneyama Y.Biochim Biophys Acta. 1983 Jun 29;745(3):219-28.Absorption and circular dichroism (CD) spectra of the Soret band, assigned as a pi-pi transition of the porphyrin pi-electron system, showed a great difference between alpha and beta subunits in the ferric state (alpha +, beta +). The nonequivalence of the spectra between alpha + and beta + subunits partly originates from the difference in the strength of the bond between heme iron and the proximal histidine. The peak positions for absorption and CD spectra of the ferric derivatives associated with F-, H2O, N-3 and CN- of the isolated subunits qualitatively correlate with the spin state of the ferric heme. The Soret absorption spectra obtained by simple addition of those for alpha + and beta + subunits are very similar to those for methemoglobin A (metHb A). On the other hand, the arithmetic means for the Soret CD spectra of alpha + and beta + subunits are different from those for metHb A. These differences were not observed between the Soret CD spectra of alpha 1 beta 1 dimer, which is predominantly present in metHb Hirose (beta 37Trp-Ser), and those of tetrameric metHb A. Therefore, the interaction between alpha 1 and beta 1 subunits to make the alpha 1 beta 1 dimer may strongly affect the CD spectral properties of alpha + and beta + subunits. The effect of the interaction between two homogeneous dimers, alpha 1 beta 1 and alpha 2 beta 2, forming a tetramer, on the Soret CD spectral properties, if any, is very small compared with that between alpha 1 and beta 1 subunits.
- ArticleThompson RE, Morrical SW, Campbell DP, Carper WR.Biochim Biophys Acta. 1983 Jun 29;745(3):279-84.The conformational changes in glucose dehydrogenase are studied as a function of temperature and guanidinium chloride (GdmCl) concentration. The data were analyzed assuming a two-conformer model which gave similar results using either circular dichroism or enzyme activity. The free energy of denaturation was 0.94 kcal/mol from specific activity and 1.64 kcal/mol from circular dichroism measurements. The mid-point of the denaturation curve was 0.65 or 0.63 M GdmCl, as determined by specific activity or circular dichroism, respectively. The transition temperature, 6.4 degrees C, is close to that of a microsomal membrane phase change, a result that is consistent with the fact that glucose dehydrogenase contains lipid materials when isolated with a non-ionic detergent such as Triton X-114. As the temperature increased, the amount of beta-pleated sheet increased, and the alpha-helical content decreased, suggested that glucose dehydrogenase contains a stable core of beta-pleated sheet.
- ArticleStone SR, Morrison JF.Biochim Biophys Acta. 1983 Jun 29;745(3):237-46.Binding theory has been developed for the reaction of an ionizing enzyme with an ionizing ligand. Consideration has been given to the most general scheme in which all possible reactions and interconversions occur as well as to schemes in which certain interactions do not take place. Equations have been derived in terms of the variation of the apparent dissociation constant (Kiapp) as a function of pH. These equations indicate that plots of pKiapp against pH can be wave-, half-bell- or bell-shaped according to the reactions involved. A wave is obtained whenever there is formation of the enzyme-ligand complexes, ionized enzyme . ionized ligand and protonated enzyme . protonated ligand. The additional formation of singly protonated enzyme-ligand complexes does not affect the wave form of the plot, but can influence the shape of the overall curve. The formation of either ionized enzyme . ionized ligand or protonated enzyme . protonated ligand, with or without singly protonated enzyme-ligand species, gives rise to a half-bell-shaped plot. If only singly protonated enzyme-ligand complexes are formed the plots are bell-shaped, but it is not possible to deduce the ionic forms of the reactants that participate in complex formation. Depending on the reaction pathways, true values for the ionization and dissociation constants may or may not be determined.
- ArticleStone SR, Morrison JF.Biochim Biophys Acta. 1983 Jun 29;745(3):247-58.The interaction of dihydrofolate reductase (EC 1.5.1.3) from Escherichia coli with dihydrofolate and folate analogues has been studied by means of binding and spectroscopic experiments. The aim of the investigation was to determine the number and identity of the binary complexes that can form, as well as pKa values for groups on the ligand and enzyme that are involved with complex formation. The results obtained by ultraviolet difference spectroscopy indicate that, when bound to the enzyme, methotrexate and 2,4-diamino-6,7-dimethylpteridine exist in their protonated forms and exhibit pKa values for their N-1 nitrogens of above 10.0. These values are about five pH units higher than those for the compounds in free solution. The binding data suggest that both folate analogues interact with the enzyme to yield a protonated complex which may be formed by reaction of ionized enzyme with protonated ligand and/or protonated enzyme with unprotonated ligand. The protonated complex formed with 2,4-diamino-6,7-dimethylpteridine can undergo further protonation to form a protonated enzyme-protonated ligand complex, while that formed with methotrexate can ionize to give an unprotonated complex. A group on the enzyme with a pKa value of about 6.3 is involved with the interactions. However, the ionization state of this group has little effect on the binding of dihydrofolate to the enzyme. For the formation of an enzyme-dihydrofolate complex it is essential that the N-3/C-4 amide of the pteridine ring of the substrate be in its neutral form. It appears that dihydrofolate is not protonated in the binary complex.
- ArticleKubilus J, Baden HP.Biochim Biophys Acta. 1983 Jun 29;745(3):285-91.The deimination of guanidyl groups of peptides, proteins and other arginine-containing compounds is catalyzed by enzymes found in mammalian brain and epidermis. In cow, the brain and epidermal enzymes differ kinetically and physically, but both may be quantitated by measuring the production of benzoyl citrulline ethyl ester from benzoyl-arginine ethyl ester. The brain enzyme has been purified to apparent homogeneity, as judged by the presence of only one 85,000 dalton band in purified preparations when examined by SDS-polyacrylamide gel electrophoresis. An antibody raised to this band precipitates pure and partially purified brain enzyme but not partially purified epidermal enzyme, using the Ouchterlony technique. The antibody bound to an insoluble matrix removes brain enzyme activity from solution but not epidermal enzyme activity. The Km of the brain enzyme for benzoyl-arginine ethyl ester is about 0.33 mM.