scholarly journals Entrapment of glucose oxidase within gold converts it to a general monosaccharide-oxidase

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yael Baruch-Shpigler ◽  
David Avnir
Keyword(s):  
Amino Acid ◽  
Glucose Oxidase ◽  
Active Sites ◽  
Activation Energies ◽  
Metallic Gold ◽  
Natural Enzyme ◽  
Metallic Biomaterial ◽  
The Difference

AbstractWe report that entrapping glucose oxidase (GOx) within metallic gold, expands its activity to become an oxidase for monosaccharides that do not have a natural enzyme with that activity—fructose and xylose—and that this entrapment also removes the enantioselectivity, rendering this enzyme capable of oxidizing the “wrong” l-enantiomer of glucose. These observations suggest that in this biomaterial adsorptive interactions of the outer regions of the protein with the gold cage, pull apart and widen the tunnel between the two monomeric units of GOx, to a degree that its stereoselectivity is compromised; then, the active sites which are more versatile than currently attributed to, are free and capable of acting on the foreign sugars. To test this proposition, we entrapped in gold l-asparaginase, which is also a dimeric enzyme (a dimer of tight dimers), and found, again, that this metallic biomaterial widens the activity of that enzyme, to include the D-amino acid counter enantiomer as well. Detailed kinetic analyses for all substrates are provided for the gold bio-composites, including determination of the difference between the activation energies towards two opposite enantiomers.

Reactivities of Piperazine-2,5-diones in Radical Bromination Reactions

1996 ◽  
Vol 49 (11) ◽  
pp. 1229 ◽  
Author(s):  
CLL Chai ◽  
DCR Hockless ◽  
AR King
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Chemical Reactivity ◽  
Trans Isomers ◽  
Radical Bromination ◽  
Conformational Effects ◽  
Cis And Trans Isomers ◽  
The Difference ◽  
Cis And Trans

The reactivities of various N,N'- diacetylated piperazine-2,5-diones towards radical bromination reactions are reported. The studies show that glycyl centres of piperazine-2,5-diones are more reactive towards radical bromination reactions compared to α-substituted amino acid centres. In addition, large differences in reactivities were observed for the cis and trans isomers of N,N'-diacetylated alanine anhydride. Single-crystal structure determination of each isomer revealed that conformational effects may account for the difference in chemical reactivity.

scholarly journals Determination of three amino acids causing alteration of proteolytic activities of staphylococcal glutamyl endopeptidases

2009 ◽  
Vol 390 (3) ◽  
Author(s):  
Takayuki K. Nemoto ◽  
Toshio Ono ◽  
Yu Shimoyama ◽  
Shigenobu Kimura ◽  
Yuko Ohara-Nemoto
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protease Activity ◽  
Binding Pocket ◽  
Catalytic Triad ◽  
Amino Acid Residues ◽  
Proteolytic Activities ◽  
Hydrophobic Amino Acids ◽  
The Difference

Abstract Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus warneri secrete glutamyl endopeptidases, designated GluV8, GluSE, and GluSW, respectively. The order of their protease activities is GluSE<GluSW<<GluV8. In the present study, we investigated the mechanism that causes these differences. Expression of chimeric proteins between GluV8 and GluSE revealed that the difference is primarily attributed to amino acid residues 170–195, which define the intrinsic protease activity, and additionally to residues 119–169, which affect the proteolytic sensitivity. Among nine substitutions present in residues 170–195 of the three proteases, the substitutions at positions 185, 188, and 189 were responsible for the changes in their activities, and the combination of W185, V188, and P189, which naturally occurs in GluV8, exerts the highest protease activity. W185 and P189 were indispensable for full activity, but V188 could be replaced by hydrophobic amino acids. These three amino acid residues appear to create a substrate-binding pocket together with the catalytic triad and the N-terminal V1, and therefore define the K m values of the proteases. We also describe a method to produce a chimeric form of GluSE and GluV8 that is resistant to proteolysis, and therefore possesses 4-fold higher activity than the wild-type recombinant GluV8.

scholarly journals Comparison of the accuracy of the hemocue glucose analyzer with the Yellow Springs Instrument glucose oxidase analyzer, particularly in hypoglycemia

2005 ◽  
Vol 153 (2) ◽  
pp. 275-281 ◽  
Author(s):  
Alexander D M Stork ◽  
Hans Kemperman ◽  
D Willem Erkelens ◽  
Thiemo F Veneman
Keyword(s):  
Glucose Oxidase ◽  
Whole Blood ◽  
Regression Analyses ◽  
Limits Of Agreement ◽  
Grid Analysis ◽  
Residual Plot ◽  
The Difference ◽  
Design And Methods ◽  
Error Grid

Objective: We aimed to assess the accuracy of the HemoCue Beta-glucose analyzer (HemoCue) and its correlation with the Yellow Springs Instrument (YSI 2300 STAT; YSI) glucose oxidase analyzer, in particular for hypoglycemic values. Design and methods: Samples were taken from 24 volunteers during hyperinsulinemic glucose clamp studies. Glucose concentrations were determined immediately with the HemoCue in whole blood and with the YSI in plasma from the same sample. After correction for the difference between whole blood and plasma, the paired plasma glucose concentrations were analyzed with various statistical methods. Results: A total of 500 paired glucose values were obtained, 209 of which were in the hypoglycemic range. Mean±s.e. values were 4.85±0.004 mmol/l for the HemoCue (range 1.87–16.17) and 4.81±0.004 mmol/l for the YSI (range 1.88–15.00; P = 0.80). In the hypoglycemic region, values were 3.26±0.004 mmol/l for the HemoCue (range 1.87–5.17) and 3.22±0.003 mmol/l for the YSI (range 1.88–4.20; P = 0.59). Regression analyses were HemoCue = 1.019(YSI) −0.0577 mmol/l, with r = 0.9787 for all values; for hypoglycemic values the HemoCue = 1.1169(YSI) −0.3393 mmol/l, with r = 0.8798. Using Altman’s residual plot, the difference was 0.03±0.0009 mmol/l, with 18 (3.6%) paired values outside the 95% limits of agreement (−0.82 to 0.89 mmol/l). In the hypoglycemic range, the difference was 0.04±0.001 mmol/l, with six (2.9%) values outside the 95% limits of agreement (−0.71 to 0.79 mmol/l). In error grid analysis, one value was in zone D (0.2%) and five values (1%) were in zone B; 98.8% were within zone A. Conclusions: Determination of glucose with the HemoCue system had very good correlation with the YSI system in a broad range of glycemia and also for hypoglycemic values. We believe that these methods can be used interchangeably for research and clinical purposes in adults.

Amino Acid Analysis of Feeds in The Netherlands: Four-Year Proficiency Study

1990 ◽  
Vol 73 (3) ◽  
pp. 394-398 ◽  
Author(s):  
Jos M Van Der Meer
Keyword(s):  
Amino Acid ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Amino Acid Analysis ◽  
Cation Exchange Resin ◽  
Photometric Detection ◽  
Accuracy And Precision ◽  
Relative Standard ◽  
The Difference

Abstract To improve accuracy and precision of amino acid analysis In 12 Dutch feed laboratories, a proficiency study was organized twice annually over a 4-year period. The method used included reflux acid hydrolysis for 22 h followed by evaporation, separation on a cation-exchange resin In an amino acid analyzer, and photometric detection after post-column derlvatlzatlon with ninhydrln. For the determination of sulfurcontaining amino acids, samples were oxidized prior to hydrolysis. For the determination of tryptophan, samples underwent an alkaline hydrolysis excluding oxygen, were separated by liquid chromatography on a Hypersil ODS analytical column, and were assayed by UV or fluorescence detection. The average relative standard deviations within (CVr) and between (CVR) laboratories were 3 and 7%, respectively. For some mixed feed samples, the results from the proficiency study were compared with those obtained by the International Analytical Group. For those samples, the relative standard deviation of the difference between IAG and Dutch groups was only 1.9%. For samples that were analyzed twice during this 4-year period, relative standard deviation of between-serles differences was only 2.1 %.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

Polypeptides Folding: Rules for the Calculation of the Backbone Dihedral Angles φ starting from the Amino Acid Sequence

2020 ◽  
Author(s):  
Michele Larocca
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Theoretical Approach ◽  
Polypeptide Chain ◽  
Hydrophobic Effect ◽  
Side Chain ◽  
Dihedral Angles ◽  
Mechanical Forces ◽  
Specific Chemical

<p>Protein folding is strictly related to the determination of the backbone dihedral angles and depends on the information contained in the amino acid sequence as well as on the hydrophobic effect. To date, the type of information embedded in the amino acid sequence has not yet been revealed. The present study deals with these problematics and aims to furnish a possible explanation of the information contained in the amino acid sequence, showing and reporting rules to calculate the backbone dihedral angles φ. The study is based on the development of mechanical forces once specific chemical interactions are established among the side chain of the residues in a polypeptide chain. It aims to furnish a theoretical approach to predict backbone dihedral angles which, in the future, may be applied to computational developments focused on the prediction of polypeptide structures.</p>

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