Reply to the comment by F. Malatesta on: “Factorizing of a concentration function for the mean activity coefficients of aqueous strong electrolytes into individual functions for ionic species” by A. Ferse and H.-O. Müller

The arguments of Malatesta (J Solution Chem 29:771–779, 2000; Fluid Phase Equil 295:244–248, 2010) exclude the experimental determination of individual ion activity coefficients. I agree that a measurement of single-ion activity coefficients is impossible. But the comment of Malatesta (J Solid State Electrochem (in press), 2011) in the connection with the purely mathematical procedure developed by Ferse and Müller (J Solid State Electrochem (in press), 2011) is senseless because there is no new aspect which is not also given in the paper of Ferse and Müller (J Solid State Electrochem (in press), 2011). All of the mentioned problems are already discussed and clarified in the publication by Ferse and Müller (J Solid State Electrochem (in press), 2011). The purely mathematical method is a possibility to obtain the concentration functions for the individual activity coefficients of the complementary ion species by factorizing a product function of the experimentally accessible concentration dependence of the mean activity coefficients to the required power.     

Reaktionsprodukte aus Antimon(V)-chlorid und N,N′-Dimethyloxamid und deren Schwingungsspektren

Reaction Products of Antimony(V) Chloride and N, N′-Dimethyloxamide and their Vibrational Spectra N, N′-Dimethyloxamide reacts with antimony(V) chloride at lower temperatures to the 1:1 resp. 1:2 addition compounds I resp. II. Pyrolysis of these compounds leads to the cyclic tetrachloroantimony(V)-N, N′-dimethyloxamides (III) resp.(V). III yields with antimony(V) chloride the 1:1 adduct IV, which is transformed to V. The vibrational spectra were assigned and discussed.     

Isolierung und Eigenschaften der sauren Phosphatase aus Ananas comosus

Zusammenfassung Im Bromelin, einer Protease aus Ananas comosus Var. Cayenne, sind einige Fremdaktivitäten enthalten. Durch Gel-Chromatographie an Sephadex G-75 läßt sich die saure Phosphatase und eine Esterase, die N-Acetyl-l-tyrosinäthylester spaltet, von der Protease abtrennen. Durch Blektrofokussierung konnte die saure Phosphatase in mindestens zwei Isoenzyme vom isoelektrischen Punkt 4, 3 bzw. 6,1 aufgetrennt werden.Die Michaelis-Konstante der sauren Phosphatase gegenüber p-Nitrophenylphosphat beträgt 0,76 · 10^–3 M (nach Lineweaver-Burk) bzw. 0,73 · 10^–3 (nach Eadie). Das pH-Optimum in Citratpuffer liegt bei pH 5,5. Es bestehen Anzeichen dafür, daß neben der höhermolekularen Phosphatase (Mol.-Gew. > 100000) auch eine niedermolekulare saure Phosphatase in den Stengeln der Ananas comosus vorkommt.In den Strünken der Ananas lassen sich erhebliche Mengen einer pflanzlichen Ribonuclease nachweisen. Dieses Enzym läßt sich durch Ionenaustausch-Chromatographie an DEAE-Cellulose von den anderen Begleitenzymen abtrennen.Eine weitere Varietät von Ananas comosus, die in Brasilien vorkommt, enthält ebenfalls große Aktivitäten an saurer Phosphatase sowie Ribonuclease, jedoch wenig Protease und keine Aktivität gegenüber N-Acetyl-l-tyrosinäthylester.

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Isolation and properties of the acid phosphatase from ananas comosus

Bromelin, a protease from pineapple (ananas comosus var. Cayenne), contains several foreign activities. Acid phosphatase and an esterase splitting N-acetyl-l-tyrosineethyl ester can be separated from the protease by gel chromatography on Sephadex G-75. The acid phosphatase can be separated into at least two isoenzymes with isoelectric points of 4.3 and 6.1, resp., by means of electrofocusing.The Michaelis constant of acid phosphatase for p-nitrophenylphosphate is 0.76×10^–3 M (according to Lineweaver-Burk) and 0.73×10^–3M (according to Eadie). The optimum pH value in citrate buffer is about 5.5. Besides the higher-molecular phosphatase (mol.-weight > 100000) also a lower-molecular acid phosphatase seems to occur in the stems of ananas comosus.Considerable amounts of a vegetable ribonuclease can be detected in the stalks of ananas. This enzym can be separated from other accompanying enzymes by ionexchange chromatography on DEAE-cellulose. Another variety of ananas comosus, occurring in Brazil, also contains high activities of acid phosphatase and ribonuclease, but only small amounts of protease and no activity towards N-acetyl-l-tyrosineethyl ester.

     

Antibacterial and antibiofilm activity of nanochelating based silver nanoparticles against several nosocomial pathogens

The emergence of multi‐drug resistant (MDR) bacteria and dynamic pattern of infectious diseases demand to develop alternative and more effective therapeutic strategies. Silver nanoparticles (AgNPs) are among the most widely commercialized engineered nanomaterials, because of their unique properties and increasing use for various applications in nanomedicine. This study for the first time aimed to evaluate the antibacterial and antibiofilm activities of newly synthesized nanochelating based AgNPs against several Gram‐positive and ‐negative nosocomial pathogens. Nanochelating technology was used to design and synthesize the AgNPs. The cytotoxicity was tested in human cell line using the MTT assay. AgNPs minimal inhibitory concentration (MIC) was determined by standard broth microdilution. Antibiofilm activity was assayed by a microtiter‐plate screening method. The two synthesized AgNPs including AgNPs (A) with the size of about 20‐25 nm, and AgNPs (B) with 30‐35 nm were tested against Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii, and Pseudomonas aeruginosa. AgNPs exhibited higher antibacterial activity against Gram‐positive strains. AgNPs were found to significantly inhibit the biofilm formation of tested strains in concentration 0.01 to 10 mg/mL. AgNPs (A) showed significant effective antibiofilm activity compared to AgNPs (B). In summary, our results showed the promising antibacterial and antibiofilm activity of our new nanochelating based synthesized AgNPs against several nosocomial pathogens.     

Total Synthesis and Structural Revision of the Antibiotic Tetrapeptide GE81112A

The total synthesis of the naturally occurring antibiotic GE81112A, a densely functionalized tetrapeptide, is reported. Comparison of spectral data with those of the natural product and the lack of biological activity of the synthesized compound led us to revise the published configuration of the 3‐hydroxypipecolic acid moiety. This hypothesis was fully validated by the synthesis of the corresponding epimer.