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Radiopharmaceuticals for Diagnostics
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Several myocardial flow tracers are available to measure cardiac perfusion. This is used to detect ischemia and infarction. Uptake mechanisms of several perfusion tracers are different [20]. Myocardial uptake of [15O]water is a result of passive diffusion and gives an excellent correlation between perfusion and tracer extraction from blood.[13N]ammonia is diffusing across the cell membrane, where it forms an equilibrium with the ammonium ion NH4+, which subsequently is trapped in the cell as it is converted to [13N]glutamine.[82Rb]RbCl2 uptake is determined by 82Rb as being an analogue of potassium, which is actively transported by the Na+/K+ ATPase-pump.
Compensatory Mechanisms in Acid–Base Disorders
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
About 75% of the metabolic acids produced in the body (approximately 50 mmol/day) are excreted as the ammonium ion, . Glutamine is deaminated in the proximal tubule, the thick ascending limb of the loop of Henle and distal tubules to form two NH+ ions and α- ketoglutarate, which is converted to two . ions. The NH+ ions are secreted into the tubular lumen by an Na+/NH+ counter-transport pump. The ions are reabsorbed into the blood (Figure 48.4).
Acid–base disturbances
Published in Martin Andrew Crook, Clinical Biochemistry & Metabolic Medicine, 2013
As the urine becomes more acid, it can be shown to contain increasing amounts of ammonium ion (NH4+). Urinary ammonia probably allows H+ secretion, and therefore HCO3− formation, to continue after other buffers have been depleted.
Untargeted lipidomic differences between clinical strains of methicillin-sensitive and methicillin-resistant Staphylococcus aureus
Published in Infectious Diseases, 2022
Philip Nikolic, Poonam Mudgil, David G. Harman, John Whitehall
Lipid species and their relative abundances were identified by a targeted lipid search using ion adduct masses on the total ion chromatograms (TICs) generated by the above UPLC-MS. This was done in Waters MassLynx v4.1. Ion adduct masses were calculated from a list of neutral masses of membrane phospholipids and glycolipids from the classes diacylglycerol (DAG), DGDG, MGDG, PG, CL and Lys-PG acquired from Hewelt-Belka et al. [22]. Protonated, ammoniated, sodiated and potassiated ion adducts were calculated by adding the mass of a hydrogen ion, ammonium ion, sodium ion and potassium ion respectively. After putative identification of a lipid species, its relative abundance was calculated from the area under the curve of the extracted ion chromatographic peak. Comparisons were made between the MSSA group and MRSA group by a Welch two sample t-test in R at a significance of p ≤ .05.
Assessment of trace element toxicity in surface water of a fish breeding river in Bangladesh: a novel approach for ecological and health risk evaluation
Published in Toxin Reviews, 2022
Md. Refat Jahan Rakib, Yeasmin Nahar Jolly, Bilkis Ara Begum, Tasrina Rabia Choudhury, Konika Jannat Fatema, Md. Saiful Islam, Mir Mohammad Ali, Abubakr M. Idris
Water samples were analyzed for common inorganic anions fluoride, chloride, nitrite, sulfate, and major cation sodium, ammonium, potassium, magnesium, and calcium by ion exchange chromatography. The concentration of anions in this study follows the decreasing order of chloride > sulfate > nitrate > fluoride. Fluoride was found in only five samples in which highest value is 0.29 ppm which is also below the safe limit set by WHO. The range of chloride, sulfate, and nitrite are 6.30–8.93, 3.475–4.255, 0.29–9.535, respectively (Table 1), and all the values are within the range of international standard and consider Halda river water is not significantly polluted by these anions. In cation test major cation like sodium, ammonium, potassium, magnesium, and calcium were analyzed in DIONEX. In all of the water samples, lithium was below its LOD value. Hardness of water is due to alkaline earth metals such as Mg and Ca ions (Abbasi 1998). Suitable hardness for fish growth is about 15 mg/L, less than 11 mg/L requires liming for higher fish production, so water having less than 5 mg/L CaCO3 cause pain, slow growth rate, and ultimately death of fish (Boyd 1981). In our study TDS value is between 18.74 and 20.30 mg/L which is within the safe range set by WHO. The highest and lowest value of ammonium ion recorded in 0.47 mg/L in station 4 and 0.28 mg/L in station 7, respectively. Sodium and potassium ions mean concentrations between the range of 8.40–10.8 ppm and 3.35–4.03 ppm was reported during the present study.
N-terminal selective conjugation method widens the therapeutic window of antibody–drug conjugates by improving tolerability and stability
Published in mAbs, 2021
Min Ji Ko, Daehae Song, Juhee Kim, Jae Yong Kim, Jaehyun Eom, Byungje Sung, Yong-Gyu Son, Young Min Kim, Sang Hoon Lee, Weon-Kyoo You, Jinwon Jung
Each of the four protein chains in an antibody terminates in an alpha amino group that represents a primary amine (Figure 1a). NTERM-conjugated ADCs were synthesized by combining an aldehyde-tagged monomethyl auristatin F (ald-MMAF) (Figure 1b) or monomethyl auristatin E (ald-MMAE) with intact antibodies via reductive alkylation reaction (Figure 1c). Since the aldehyde group can act as an electrophile, it can react with amines that have lone-pair electrons. However, the aldehyde group cannot react with an ammonium ion because the ion has no lone pair electrons. Additionally, since the pKa of N-terminal α-amine is 2–3 units smaller than that of lysine ε-amine, the primary amine of the N-terminus comprises the dominant population of reactive amine over lysine ε-amine that mostly represents an ammonium ion at pH below 7. Grimsley et al. summarized pKa values of the ionizable groups in folded proteins from the literature, and the pKa was 7.7±0.5 for the N-terminus and 10.5±1.1 for lysines.13 At pH 5.49, the ratio of amine and ammonium ion becomes 1:102.21 (162-fold difference) for the N-terminus, and 1:105.01 (102,330-fold difference) for lysine ε-amine. Therefore, the alkylation reaction will happen preferentially on the N-termini of heavy and light chain of the antibody. The reaction then generates reversible, unstable imine bonds. Therefore, the imine bonds need to be reduced selectively by NaBH3CN to form a stable amine bond (Figure 1c).