Biochemistry of Buffering Capacity and Ingestion of Buffers In Exercise and Athletic Performance
Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse in The Routledge Handbook on Biochemistry of Exercise, 2020
These findings question the efficacy and mechanism of action of sodium citrate. A possible explanation is that an inhibitory effect of increased intracellular citrate counteracts the increase in extracellular buffering capacity (62). Citrate can allosterically inhibit the rate-limiting glycolytic enzyme, phosphofructokinase, and thus reduce adenosine triphosphate production. A further issue could be the timing of ingestion, since most studies included in the meta-analysis supplemented sodium citrate 90 to 120 minutes prior to exercise (16). As discussed, this may be a sub-optimal strategy as it does not allow for peak blood alkalosis and coincides with greater side effects (124). Thus, improvements in exercise performance may be more apparent with a longer period between sodium citrate ingestion and the start of the task, but this remains to be experimentally confirmed.
The Modification of Carboxyl Groups
Roger L. Lundblad, Claudia M. Noyes in Chemical Reagents for Protein Modification, 1984
Other approaches to the conversion of carboxylic acid functional groups to methyl or ethyl esters have been considered. Trialkyloxonium fluoroborate salts (Figure 2) have proved effective. Raftery and co-workers used triethyloxonium fluoroborate to modify the β-carboxyl groups of an aspartic residue essential for the enzymatic activity of lysoszyme.17,18 Paterson and Knowles19 used trimethyloxonium fluoroborate to determine the number of carboxyl groups in pepsin which are essential for catalytic activity. This article discusses in some depth the rigorous precautions necessary for the preparation of this reagent. This reagent is highly reactive and considerable care is required for its introduction into the reaction mixture containing protein. The reaction is performed at pH 5.0 (0.020 M sodium citrate, pH maintained at 5.0 with 2.5 M NaOH). These investigators also report the preparation of the 14C-labeled reagent from sodium methoxide and [14C] methyliodide.
Urolithiasis
Manit Arya, Taimur T. Shah, Jas S. Kalsi, Herman S. Fernando, Iqbal S. Shergill, Asif Muneer, Hashim U. Ahmed in MCQs for the FRCS(Urol) and Postgraduate Urology Examinations, 2020
Urinary alkalinisation is important in the management of patients with both cystine stones and uric acid calculi. Sodium bicarbonate and potassium citrate are commonly used agents. Sodium bicarbonate is taken by mouth (325 to 2000 mg orally 1 to 4 times a day) and the dose titrated according to response. Common side effects include bloating and flatulence, but it may lead to salt and water retention and can worsen hypertension. The high sodium intake can lead to increased calcium absorption from the bowel and may increase the risk of calcium oxalate stones. Potassium citrate solution (10–20 mL three times per day) is again titrated according to urinary pH. It has a foul taste and compliance is less than 50%. Potassium citrate tablets are an alternative but are not available in the United Kingdom. Sodium citrate may also be used as a more palatable alternative. The target pH reflects the pKa of the stone constituents (for example, cystine – pKa 8.3, urate – pKa 5.8).
Clot activators and anticoagulant additives for blood collection. A critical review on behalf of COLABIOCLI WG-PRE-LATAM
Published in Critical Reviews in Clinical Laboratory Sciences, 2021
G. Lima-Oliveira, L. M. Brennan-Bourdon, B. Varela, M. E. Arredondo, E. Aranda, S. Flores, P. Ochoa
Sodium citrate is commonly used as a solution of dihydrate trisodium citrate. It is a nontoxic anticoagulant that converts Ca++ ions to the non-ionized form and prevents coagulation (Figure 4) [92]. In the clinical laboratory, it is employed mainly for preventing blood coagulation for hemostasis testing, platelet studies, and erythrocyte sedimentation rate. While additives may be liquid or dry, the latter form is preferable because the water of the liquid additives can diffuse out the plastic and jeopardize the blood/additive ratio. However, buffered sodium citrate is available only in liquid form. Therefore, manufacturers of evacuated tubes have developed a “double wall” tube system to avoid water loss and to maintain the quality of their product. Briefly the sodium citrate used in evacuated tubes has a pH ∼ 5.8 that requires approximately −40 °C in the crystallization phase of lyophilization, making the process of lyophilization of this additive in evacuated tubes impractical [93].
Alternative processing technology for the preparation of carbonized Zingiberis Rhizoma by stir-frying with sand
Published in Pharmaceutical Biology, 2020
Shen Mei-Yu, Wang Jia-Li, Shi Hai-Pei, Yan Hui, Chen Pei-Dong, Yao Wei-Feng, Bao Bei-Hua, Zhang Li
Dried gingers were purchased from Anhui Bozhou Medicinal Materials Market and identified as dried roots of Zingiber officinale by Professor Yan Hui, Department of Traditional Chinese Drug Identification, Nanjing University of Chinese Medicine, Nanjing, China. Voucher specimens (Nos. GJ20171010-01 to GJ20171010-10) were preserved in NJUCM herbaria. Methylene blue was purchased from China Pharmaceutical (Group) Shanghai Chemical Reagent Company. Gallic acid reference standard (Batch No. 19630) was purchased from Shanghai Jingchun Reagent Co., Ltd. The reference standards of Zingerone (JBZ180323-032), 6-gingerol (JBZ180110-027), 8-gingerol (JBZ180209-028), 6-shogaol (JBZ180208-030), 8-shogaol (JBZ171129-03) and 10-shogaol (JBZ180108-044) were purchased from Nanjing Jinyibai Bio Technology Co., Ltd. (Nanjing, Jiangsu, China) (all purity ≥98%, by HPLC). 10-Gingerol (P2DN6F6295) was purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China) (purity ≥98%, by HPLC). Acetonitrile and methanol were chromatographically pure (Jiangsu Hanbang Technology Co., Ltd., Huaian, Jiangsu, China). Ultrapure water was obtained with a Milli-Q ultrapure water system (Millipore Inc., USA). Sodium citrate (Batch No. 20170407) was purchased from Tianjin Jinhui Taiya Chemical Reagent Co., Ltd. (Tianjin, China)
Using flow cytometry to monitor glycoprotein IIb-IIIa activation
Published in Platelets, 2018
Despite the wealth of literature on determination of activated GPIIb-IIIa using FITC-PAC1, there are a number of possible pitfalls that can cause difficulties if not considered. First is the choice of anticoagulant if the goal is to establish a whole blood assay. Sodium citrate (3.2%) is used most often. Although citrate chelates calcium, sufficient free calcium remains to fully support binding of FITC-PAC1 to activated platelets. This is in direct contrast to ethylenediaminetetraacetic acid (EDTA), which is not recommended for this assay (11, 13). PPACK (prolyl-prolyl-alanyl-chloromethyl ketone) and hirudin are direct thrombin inhibitors, thereby allowing anticoagulation while keeping plasma calcium at its physiologic level. This important difference in free calcium level was found to cause an approximate two-fold difference in the potency of eptifibatide for inhibition of platelet aggregation and corresponded to a nearly 5-fold difference in the concentration of eptifibatide required for 50% inhibition of PAC1 binding (eptifibatide IC50 for PAC1 binding was 31.7 ± 9.0 nM in citrate, 143 ± 87 nM in PPACK) (51). Heparin also maintains plasma calcium at physiologic levels, but binds to and transiently activates platelets (52) and is therefore not recommended as an anticoagulant for tests of activated GPIIb-IIIa by flow cytometry (53). Platelet reactivity to agonists is also affected by the choice of anticoagulant as discussed extensively in a recent review (54).
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