(v. i.) To be as a fact and not as a mode; to have an actual or real being, whether material or spiritual.
(v. i.) To be manifest in any manner; to continue to be; as, great evils existed in his reign.
(v. i.) To live; to have life or the functions of vitality; as, men can not exist water, nor fishes on land.
Example Sentences:
(1) One hundred and twenty-seven states have said with common voice that their security is directly threatened by the 15,000 nuclear weapons that exist in the arsenals of nine countries, and they are demanding that these weapons be prohibited and abolished.
(2) The only other evidence of Kopachi's existence is the primary school near the memorial.
(3) Subsequently, the study of bundle branch block and A-V block cases revealed that no explicit correlation existed between histopathological changes and functional disturbances nor between disturbances in conduction (i.e.
(4) It has recently been suggested that procaine penicillin existed in solution in vitro and in vivo as a "procaine - penicillin" complex rather than as dissociated ions.
(5) The data suggest that major differences may exist between ruminants and non-ruminants in the response of liver metabolism both to lactation per se and to the effects of growth hormone and insulin.
(6) The obvious need for highly effective contraception in women with existing disorders of glucose metabolism has led to a search for oral contraceptive (OC) regimens for such women that are efficient but without unacceptable metabolic side effects.
(7) These results are discussed in relation to the possible existence of enzyme-bound intermediates of nitrogen fixation.
(8) Psychiatry unlike philosophy (with its problem of solipsism) recognizes the existence of other minds from the nonverbal communication between doctor and patient.
(9) Over the past decade the use of monoclonal antibodies has greatly advanced our knowledge of the biological properties and heterogeneity that exist within human tumours, and in particular in lung cancer.
(10) This suggests that a physiological mechanism exists which can increase the barrier pressure to gastrooesophageal reflux during periods of active secretion of the stomach, as occurs in digestion.
(11) After four years of existence, many evaluations were able to show the qualities of this system regarding root canal penetration, cleaning and shaping.
(12) The authors conclude that H. pylori alone causes little or no effect on an intact gastric mucosa in the rat, that either intact organisms or bacteria-free filtrates cause similar prolongation and delayed healing of pre-existing ulcers with active chronic inflammation, and that the presence of predisposing factors leading to disruption of gastric mucosal integrity may be required for the H. pylori enhancement of inflammation and tissue damage in the stomach.
(13) Elongation of existing RNA primers by the human polymerase-primase was semi-processive; following primer binding the DNA polymerase continuously incorporated 20 to 50 nucleotides, then it dissociated from the template DNA.
(14) Richard Hill, deputy chief executive at the Homes & Communities Agency , said: "As social businesses, housing associations already have a good record of re-investing their surpluses to build new homes and improve those of their existing tenants.
(15) The relative strength of the progressions varies with excitation wavelength and this, together with the absence of a common origin, indicates the existence of two independent emitting states with 0-0' levels separated by either 300 or 1000 cm-1.
(16) Participants were selected from existing classes forming a weight training, aerobic exercise and activity control group.
(17) Neurotensin (NT) is an endogenous brain tridecapeptide for which high affinity binding sites exist in the central nervous system.
(18) These results are interpreted in terms of the accessory binding site theory of Ariëns, and suggest the existence of different accessory binding sites on the Ascaris GABA receptor.
(19) Achilles tendon overuse injuries exist as a spectrum of diseases ranging from inflammation of the paratendinous tissue (paratenonitis), to structural degeneration of the tendon (tendinosis), and finally tendon rupture.
(20) Little difference exists between the proportion of programs that offer training in first-trimester techniques and the proportion that train in second-trimester techniques.
Tautomerism
Definition:
(n.) The condition, quality, or relation of metameric substances, or their respective derivatives, which are more or less interchangeable, according as one form or the other is the more stable. It is a special case of metamerism; thus, the lactam and the lactim compounds exhibit tautomerism.
Example Sentences:
(1) The coupled dienone-phenol re-arrangement and keto-enol tautomerism of this quinone methide produce the observed 3,4-dihydroxybenzaldehyde.
(2) On the other hand, results indicate that the protonation of formycin and its derivatives at the N1 atom leads to a change in their tautomeric preference from N7-H to N8-H.
(3) The inhibitor trapping system, however, prevents the inactivation of succinate dehydrogenase under the conditions when the rate of tautomeric oxaloacetate enol in equilibrium oxaloacetate ketone interconversion is high.
(4) In contrast, equilibria of ring chain tautomerism and covalent hydration of aldoses are almost completely insensitive to the polarity of their surroundings.
(5) The importance of both tautomerism and protonation reactions in the mechanism of action of adenosine deaminase is studied by means of a quantitative structure activity relationships strategy.
(6) The possibility that this product is an equilibrium mixture with the tautomeric 4-hydroxycyclophosphamide has not been as yet defintely ruled out.
(7) In addition to being a possible mechanism for alteration of hydrogen bonding in oxidized DNA, this type of interaction gives a better understanding into N7-N9 tautomerism of adenine.
(8) The product 3-fluorooxalacetate is thus released from phosphoenolpyruvate carboxykinase as the keto form and is reduced more rapidly by reduced nicotinamide adenine dinucleotide with malate dehydrogenase than by the occurrence of tautomerization.
(9) These results strongly suggest that the anomeric, epimeric, and tautomeric form of the sugar phosphate substrates favored by both enzymes is the beta-D-fructofuranose form.
(10) Tautomerization of DOPA quinone to dehydroDOPA may thus be a factor in the sclerotization of natural structures incorporating DOPA containing proteins.
(11) For the complex formed between [5,5-2H,5-13C]ALA and methyl methanethiosulfonate (MMTS) modified PBG synthase, which does not catalyze PBG formation but can form a Schiff base adduct, the chemical shift of 44.2 ppm (line width 92 Hz) identifies an imine structure as the predominant tautomeric form of the Schiff base.
(12) delta 5-3-Ketosteroid isomerase (EC 5.3.3.1) catalyzes the isomerization of delta 5-3-ketosteroids to delta 4-3-ketosteroids by a conservative tautomeric transfer of the 4 beta-proton to the 6 beta-position with Tyr-14 as a general acid and Asp-38 as a general base [Kuliopulos, A., Mildvan, A. S., Shortle, D., & Talalay, P. (1989) Biochemistry 28, 149-159].
(13) The results are consistent with evidence for the formation of the first tetrahydropterin intermediate by a tautomerization without any requirement for NADPH.
(14) Its function is probably to maintain the orientation and tautomeric state of the imidazole ring of histidine-159.
(15) This suggests that a stable AP:C base mispair via two hydrogen bonds can be formed with the imino tautomer of C. These results stress the importance of the imino form of C in AP-induced mutagenesis and support the 'trigger mechanism', in which formation of one hydrogen bond between AP and C is considered to stimulate the tautomeric shift of AP or C. The calculated relative stabilities of various base pairs and mispairs were in good agreement with experimental findings.
(16) Whereas O6-MeGua did not form hydrogen bonds with cytosine (via usual, wobble, or unusual tautomeric structures), it did form a 1:1 hydrogen-bonded complex with protonated cytosine.
(17) Amide-imide tautomerism enables a cleanup of the extract.
(18) Ultraviolet and infrared spectrophotometric techniques have been utilized to demonstrate that the monoanionic form of 2-thiouracil in aqueous medium consists of an equilibrium mixture of two tautomeric monoanions, one due to dissociation of the N1 proton, the other to dissociation of the N3 proton, in the approximate ratio 1:1.
(19) Combined use of mass spectroscopy and 1H- and 13C-NMR spectroscopy established that it is the 4,8-anhydro derivative of N-acetylneuraminic acid and that in solutions it exists in two tautomeric forms.
(20) As a result of a concerted proton (tautomeric) shift in the linked residues of the hydrogen-bond chain, which includes the bound molecule, a charge separation occurs.