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The Modification Of Tyrosine
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
Iodination can also be accomplished by peroxidase per H2O2 per Nal. A recent procedure was described for the modification of tyrosyl residues in insulin.20 In these studies 20 mg of porcine insulin in 20 ml 0.4 M sodium phosphate, 6.0 M urea, pH 7.8 was combined with 10 ml Na125I (1 mCi) and 3.6 mg urea, and H202 (5 μl 0.3 mM solution) and peroxidase (Sigma, 0.2 mg/ml; 5 μl) added. The preparative reaction was terminated by dilution with an equal volume of 40% (w/v) sucrose. It is of interest to note that the enzyme-catalyzed iodination proceeds with efficiency in 6.0 M urea. Iodination of tyrosyl residues in peptides and proteins can also be accomplished with chloramine T.21,22 In a recent study,23 the solution structure of insulin-like growth factor was investigated by iodination of tyrosyl residues mediated by either chloramine T or lactoperoxidase. Chloramine T was more effective than lactoperoxidase.
Methods of Protein Iodination
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
The compound is iodinated by using chloramine-T. Since it is relatively stable in aqueous solutions, the iodination can be conducted over a longer period of time (15 min) as compared to the Bolton-Hunter procedure. Partly because of that, and partly with the help of carrier Nal, the compound is converted nearly quantitatively to its diiodo derivative. The diiodoimidoester is less soluble at neutral pH than its nonhalogenated counterpart, whereby it can be separated from the other components of the reaction mixture by precipitation brought about by pH adjustment to neutrality. The disubstituted compound has a characteristic absorption spectrum with maxima at 240 and 340 nm.
Nonisotopic Labeling
Published in Lelio G. Colombetti, Principles of Radiopharmacology, 2019
This method uses Chloramine-T to activate Na 125I into an oxidized, reactive state.18,19 It is the most widely used method for labeling proteins because of its speed and relative simplicity. Small quantities of proteins may be iodinated to high specific activities for use as in vitro reagents. Usually, the protein solution, the isotope, and a small amount of buffer, all in micro volumes, are placed in a tiny reaction vessel and a solution of fresh Chloramine-T is quickly added. After a time period varying from a few seconds to a few minutes, depending on the protein and its ease of iodination, the reaction is terminated by adding a small quantity of a bisulfite solution. Reaction volumes are kept as small as practicable. In current practice, the amount of Chloramine-T has been drastically reduced from that used in the original reference, and one normally uses only enough excess over the stoichiometric amount to give the desired iodine incorporation.20 For best results the reaction mixture is diluted with a carrier protein and carrier iodide and is then purified quickly on a chromatographic column to remove any components that might damage the proteins. For best yields the pH is maintained at about 7.5.21 In spite of the careful attention to detail, a few sensitive proteins may be damaged by the Chloramine-T procedure.
New frontier radioiodinated probe based on in silico resveratrol repositioning for microtubules dynamic targeting
Published in International Journal of Radiation Biology, 2023
Ashgan F. Mahmoud, Mohamed H. Aboumanei, Walaa Hamada Abd-Allah, Mohamed M. Swidan, Tamer M. Sakr
Chloramine-T is acting as a suitable oxidizing agent and commonly utilized in the electrophilic substitution reactions such as radioiodination due to its ability to oxidize the radioiodine to the oxidative state (iodonium, I+) which is the reactive form capable of achieving an electrophilic substitution reaction (Vértes et al. 2010; Motaleb et al. 2012). Hence, the concentration of the oxidizing agent, CAT, was addressed as a critical parameter in the radioiodination reactions which is clearly demonstrated in Figure 2(a). The radiolabeling yield was significantly varied by increasing the CAT concentration from 10 to 100 µg/mL as it addressed 68 ± 1.55 and 94.6 ± 1.66, respectively. Further excess of the CAT concentration above the optimized one (100 µg/mL) resulted in lowering the radiolabeling yield till became 72.6 ± 1.86 at 150 µg/mL. This radiolabeling yield dwindling may be attributed to the high reactivity of CAT at higher concentrations warranting resveratrol polymerization and/or chlorination which are considered as undesirable by-products (Swidan et al. 2014, 2015; Aboumanei and Mahmoud 2020).
Myricetin derivative-rich fraction from Syzygium malaccense prevents high-fat diet-induced obesity, glucose intolerance and oxidative stress in C57BL/6J mice
Published in Archives of Physiology and Biochemistry, 2023
Devi Nallappan, Kien Chai Ong, Uma Devi Palanisamy, Kek Heng Chua, Umah Rani Kuppusamy
The protein carbonyl content in urine and tissue homogenates were determined as described by Kanagasabapathy et al. (2013). Briefly, the fresh AOPP reagent solution was prepared by mixing phosphate-buffered saline (PBS), glacial acetic acid (50% v/v) and potassium iodide (1.16 M) at the ratio of 81:15:4. The reagent solution (200 µL) was added to 18 µL of the sample, then the absorbance was measured immediately at 340 nm against the blank. Water and PBS were used as blank for urine and tissue homogenate samples, respectively. A known concentration of the chloramine-T solution (0 to 500 µM) was used as a standard and the result was calculated and expressed as µmol/L chloramine-T equivalent for urine samples and as µmol chloramine-T equivalent/g tissue for tissue homogenates.
Management and prevention of drug resistant infections in burn patients
Published in Expert Review of Anti-infective Therapy, 2019
Roohi Vinaik, Dalia Barayan, Shahriar Shahrokhi, Marc G Jeschke
However, while daily cleansing and burn eschar debridement may be beneficial, routine implementation of hydrotherapy is not employed due to increased rates of infection [71,73]. Embil et al. reported a multi-institution outbreak of MRSA, demonstrating that cultures obtained from the hand-held shower and stretcher for showering in a hydrotherapy room were positive for the outbreak strain. Furthermore, replacement of stretcher showering with bedside sterile compresses ended the outbreak, highlighting the risk of utilizing hydrotherapy equipment [73]. Nosocomial transmission of microorganisms can occur via contaminated tank water, aerators, or health care personnel directly. As a preventative measure, sodium hypochlorite and chloramine-T disinfectants are typically added to tank water to decrease microbial load [74]. While this strategy may be effective in decreasing gram-negative contaminants, outbreaks of drug-resistant organisms were still reported. Common equipment such as tubs and spray tables are difficult to clean between patient use, especially when colonized with gram-negative organisms that form a resistant biofilm. This allows bacterial organisms to colonize water pipes, drains, and shower tables despite use of disinfectants. While minimizing bathing frequency and maintaining sterile conditions could minimize risk of infection and allow safe implementation, increased costs, time for dressing changes, and risk of spreading microbes from one patient to another limits the use of hydrotherapy [75]. As a result, hydrotherapy currently has no role in burn patient management.