ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
Isotopes are variants of the same ELEMENT. Every ATOM of a particular element contains the same number of protons, but some have more neutrons (and therefore weigh more; see ATOMIC WEIGHT). Isotopes are very common in nature: most elements of biological importance have several isotopes. For example, carbon always has 6 protons, but can have 6, 7 or 8 neutrons. While these all have different atomic weights they are nevertheless isotopes of each other. Isotopes can be stable or radioactive: stable isotopes are those whose atomic nuclei remain stable: they have a number of protons and neutrons and retain those numbers. A radioactive isotope (or RADIOISOTOPE) is one in which the atomic nucleus decays, releasing protons and energy and, because protons are lost, turning the element from one thing to another. There is a received style for presenting elements that indicates their nuclear composition: carbon-12 has a total of 12 neutrons and protons. Since all forms of carbon have 6 protons, it follows that carbon-12 (or 12C, or 12/6C} has 6 neutrons. Carbon-13, by the same arithmetic, has 7 neutrons, carbon-14 has 8. Carbon-12 and carbon-13 are stable; carbon-14 is radioactive and decays over time to form nitrogen. Radioisotopes are useful in a variety of neuroscientific procedures: see for example, AUTORADIOGRAPHY; FUNCTIONAL NEUROIMAGING; RADIOIMMUNOASSAY; RADIOLABEL.
Introduction and Method
Christopher Cumo in Ancestral Diets and Nutrition, 2020
C3 and C4 pathways use different carbon isotopes. Isotopes of an element have identical chemical properties because the number of protons is constant but different masses because the numbers of neutrons differ. Most carbon, known as 12C, has 12 grams per mole, with a mole being a standard, huge number of atoms (6 × 1023). These 12 grams, the atomic mass, are the sum of carbon’s six protons and six neutrons in its nucleus. Carbon (13C) with seven neutrons has an atomic mass of thirteen, and carbon (14C) with eight neutrons has a mass of fourteen. Of these isotopes, 12C and 13C are stable and far more abundant in nature than 14C. Being unstable 14C decays into nitrogen. Being more numerous, 12C and 13C are available to form molecules, including the carbon dioxide that plants absorb, with other elements. Because C3 plants absorb more 12C than do C4 plants, whatever eats more C3 than C4 plants fixes more 12C in bones and teeth. Consequently, people who ingest more C3 than C4 plants or more animals with this pattern of consumption yield skeletons and teeth with greater ratios of 12C to 13C. Such information, for example, distinguishes barley from millet eaters.
Monitoring in neurotrauma
Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor in Essentials of Anesthesia for Neurotrauma, 2018
Emerging techniques for the global intermittent assessment of various aspects of cerebral metabolism show promise. Two paramagnetic isotopes require mentioning. In particular, the use of 13carbon (13C) labeled substrates within MRS.69 The ability to label various metabolic substrates and intermediaries exists. This potentially allows for comment on various aspect, of cerebral glucose and lactate metabolism. In addition, 31phosporus (31P) labeled compounds allow us to potentially make comments on cerebral energy stores.69 Both of these techniques are considered experimental.
Novel sulindac derivatives: synthesis, characterisation, evaluation of antioxidant, analgesic, anti-inflammatory, ulcerogenic and COX-2 inhibition activity
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Mashooq A. Bhat, Mohamed A. Al-Omar, Nawaf A. Alsaif, Abdulrahman A. Almehizia, Ahmed M. Naglah, Suhail Razak, Azmat Ali Khan, Naeem Mahmood Ashraf
The acetohydrazide (III) was used as a starting material for the synthesis of various substituted sulindac hydrazone derivatives (1 – 25). The acetohydrazide (III) was reacted substituted benzaldehydes in ethanol and glacial acetic acid as a catalyst. The acetohydrazide was characterised by the appearance of singlet peak for the –NH2 protons at δ 3.38 ppm and broad singlet for the CONH proton at δ 9.30 ppm. The disappearance of NH2 protons at δ 3.38 ppm confirmed the structures of sulindac hydrazones. Carbon-13 NMR confirmed all the carbon atoms of the synthesised compounds (1‒25). Mass spectroscopy confirmed the molecular weights of compounds. All the compounds were characterised by their molecular ion peaks. The three methyl protons of the indene moiety appeared in the range of δ 2.18‒2.23 ppm. The three protons of –SOCH3 appear at δ 2.81‒2.83 ppm. The aromatic protons appeared in the range of δ 6.71‒8.24 ppm. Protons of the N=CH appeared as a singlet in the range of δ 7.92‒8.52 ppm and the proton of CONH appeared as broad singlet at δ 9.30‒11.80 ppm.
Comparative study of the antidiabetic potential of Paederia foetida twig extracts and compounds from two different locations in Malaysia
Published in Pharmaceutical Biology, 2019
Dai Chuan Tan, Ku Idayu Idris, Nur Kartinee Kassim, Pei Cee Lim, Intan Safinar Ismail, Muhajir Hamid, Rou Chian Ng
The melting point of scopoletin was determined using the Barnstead Electrothermal IA 9000 series digital melting point apparatus equipped with a microscope. Perkin Elmer Fourier-Transform Infrared (FTIR) spectrophotometer which applied Universal Attenuated Total Reflection (UATR) was used to determine infrared spectra of the samples. The infrared spectra of the sample were observed in the range 280–4000 cm−1. The mass spectrum of the compound was recorded by using a Shimadzu Gas Chromatography–Mass Spectrometer (GC–MS) model QP5050A with BPX5 (5% phenylmethylsilane) capillary column (30 × 250 μm × 0.25 μm). A JEOL Fourier-Transform Nuclear Magnetic Resonance (FT-NMR) spectrometer was used to determine proton (1H) and carbon-13 (13C) Nuclear Magnetic Resonance (NMR) spectra of the compound. 1H NMR was measured at 500 MHz while 13C NMR was measured at 125 MHz. Two-dimensional (2D) NMR including correlated spectroscopy (COSY), heteronuclear multiple bond connectivity by heteronuclear multiple bond correlation (HMBC) and heteronuclear multiple quantum correlation (HMQC) were also done. The antidiabetic and antioxidant assays were performed using the µ-QUANT model microplate reader.
Acoustic mist ionization mass spectrometry (AMI-MS) as a drug discovery platform
Published in Expert Opinion on Drug Discovery, 2019
Ian Sinclair, Gareth Davies, Hannah Semple
In the case of target molecules with molecular weights around 400 Da that contain ~25 carbon atoms, the main C12 peak will contain over 70% of the ion area so the inclusion of the first C13 peak is not critical. However, in molecules with large numbers of carbons, e.g. peptides with molecular weights in excess of 1500 Da, there may be over 100 carbon atoms in the structure. With each carbon atom having a 1.1% chance of being a carbon-13 there will be less than 40% of the ion area in the C12 peak; these molecules will have considerable ion currents not only where one C13 is included but also where two and three C13 atoms are present. Utilizing the data from multiple peaks of the same chemical species improves sensitivity and reduces variability from the ion counting detector.
Related Knowledge Centers
- Proteomics
- Carbon
- Atomic Nucleus
- Stable Isotope Labeling By Amino Acids In Cell Culture
- Urea Breath Test
- C3 Carbon Fixation
- Isotopic Signature
- Kinetic Fractionation
- Δ13C
- Carbon-13 Nuclear Magnetic Resonance