Joseph R. Guarini

Bio: Joseph R. Guarini is an academic researcher from University of Wisconsin-Madison. The author has contributed to research in topics: Solubility & Aqueous solution. The author has an hindex of 1, co-authored 1 publications receiving 22 citations.

Metal chelates of streptomycin.

Abstract: Streptomycin has been found to undergo chelation with several metals in aqueous solution. Evidence for chelate formation is provided by a drop in pH during the formation, production of characteristic colors, decreased solubility in water, and absence of metal ions in the solution. The copper chelate, found to be relatively uncontaminated with metal hydroxide, exhibited more prolonged blood levels in guinea pigs than streptomycin sulfate, but also a greater toxicity.

Metal binding by pharmaceuticals. Part 1. Copper(II) and zinc(II) interactions following ethambutol administration.

Abstract: Formation constants for copper(II) and zinc(II) complexes of dextro-2,2′-(ethylenediimino)-di-1-butanol (ethambutol) and its metabolic oxidation product, 2,2′-(ethylenediimino)-dibutyric acid (EDBA) have been measured potentiometrically at 37°C, I=0.15 mol dm−3 [NaCl]. The constants are used in computer models to assess the extent of the formation of these complexes in vivo. These simulations indicate that whereas ethambutol forms metal complexes only to a limited extent in vivo, EDBA competes effectively under physiological conditions for copper(II) and zinc(II). This study suggests that zinc(II) binding by EDBA may account for a number of side effects of ethambutol treatment.

Metal binding tendencies of various antibiotics

Abstract: A method to determine the presence of metal-drug complexes in dilute solutions is described. Using this method cycloserine was found to complex with cupric, nickelous, zinc and cobalt ions; streptomycin and novobiocin complexed with cupric ions; erythromycin complexed with cobalt ions, and chloramphenicol exhibited no metal binding tendencies. Various penicillins were found to interact with zinc and cupric ions. Preliminary investigations suggest that cupric ions, rather than simply complexing with penicillin as suggested by previous workers, promote the degradation of penicillin to penicilloic acid. Evidence is presented to confirm the presence of penicilloic acid in reaction mixtures initially containing penicillin G or V and cupric ions, and to establish that the reaction follows second order kinetics and ceases when all available cupric ion has been consumed. Good correlation was noted for these results and previous work which showed the effects of metal ions on the antibacterial properties of penicillin.

Enzymatic properties of a phage-induced lysin affecting group A streptococci.

Abstract: Doughty, C. C. (University of Illinois College of Medicine, Chicago) and James A. Hayashi. Enzymatic properties of a phage-induced lysin affecting group A streptococci. J. Bacteriol. 83:1058-1068. 1962.-Phage-induced lysis of group C streptococci releases into the medium a lysin which completely lyses group A streptococci. Partial purification of the lytic activity yields 47% of the original activity with a 17-fold purification. The activity was assayed by observing lysis of group A streptococci under standard conditions. The optimal pH range for lysis is from 6.0 to 6.7. A monovalent cation requirement satisfied by Na(+), K(+), or Li(+) is shown by the lysin. Lysis is stimulated by ethylenedi-aminetetraacetic acid (EDTA), chlortetracycline, streptomycin, and penicillin. It is inhibited by p-hydroxymercuribenzoate (pHMB), and the inhibition is reversed by cysteine. Other inhibitors include ristocetin A and specific antisera against the lysin. Isolated group A streptococcal cell walls are partially lysed by massive amounts of lysin. This partial lysis is not affected by EDTA, pHMB, chlortetracycline, streptomycin, or ristocetin A. It is concluded that the enzymatic process of lysis of isolated cell walls is not identical to the more complex process resulting in lysis of intact cells.