Temporary Blocking Research Articles

The photochemistry of carbohydrate derivatives. Part 5. Synthesis of methyl 2,3-di-O-(β-D-glucopyranosyl)-α-L-fucopyranoside and methyl 2,3-di-O-(β-D-galactopyranosyl)-α-L-fucopyranoside using photolabile O-(2-nitrobenzylidene) acetals as temporary blocking groups

The branched trisaccharide derivatives (6) and (12) named in the title have been synthesised from methyl 3,4-O-(2-nitrobenzylidene)-α-L-fucopyranoside (1) using the 2-nitrobenzylidene residue as a temporary blocking group.

Stereoselective syntheses of 1,2-cis- and 1,2-trans-d-mannopyranosides

3,4,6-Tri-O-allyl-β-d-mannose 1,2-(methyl orthoacetate) has been prepared from the corresponding tri-O-acetyl derivative and used as a precursor for stereo-controlled synthesis of both the 1,2-cis- and trans-d-mannopyranosides. The allyl groups were selected and tested as temporary blocking groups which allow suitable deprotection under mild conditions following glycosidation. Hydrolysis of the orthoester ring afforded 3,4,6-tri-O-allyl-d-mannose. The latter was converted into 3,4,6-tri-O-allyl-2-O-mesyl-α-d-mannopyranosyl chloride, whose coupling with methanol and cyclohexanol afforded stereoselectively the β anomers as the major products. Methanolysis of the orthoester afforded the α anomer as the major product. The determination of the anomeric configuration is discussed and the 1H-n.m.r. and 13C-n.m.r. spectral data are correlated.

New reagents for the introduction of the thiomethyl group at sulfhydryl residues of proteins with concomitant spectrophotometric titration of the sulfhydryls: Methyl 3-nitro-2-pyridyl disulfide and methyl 2-pyridyl disulfide

Two new reagents for the titration of sulfhydryl groups in peptides and proteins and for their temporary blocking with the thiomethyl group have been developed. The sulfhydryl groups in cysteine, glutathione, and papain react quantiatively under mild conditions with these reagents, methyl 3-nitro-2-pyridyl disulfide and methyl 2-pyridyl disulfide, with concomitant methanethiolation and without the need to employ a large excess of reagent. Because of the chromophoric properties of the 3-nitro-2-thiopyridone and 2-thiopyridone products, spectrophotometric titration of the sulfhydryl groups can be carried out, accompanying their methanethiolation. The modification of the sulfhydryl groups in peptides and proteins with thiomethyl is rapidly and completely reversible upon addition of thiols such as l-cysteine.

Effect of anodal polarization of deep brain structures on spatial synchronization of cortical potentials during defensive conditioning in rabbits.

1. Reversible blocking of some nonspecific thalamic and hypothalamic nuclei differs in its effect on two types of spatial synchronization of cortical potentials (SSCP) formed during defensive conditioned reflex (DCR) formation: Specific local SSCP and conditionedreflex movements disappear, whereas global SSCP remains virtually unchanged under these circumstances in interstimulus periods. 2. By modifying their functional state of these nuclei by anodal polarization it is possible to influence the rate of DCR formation. The effect of polarization depends on the structure to be stimulated and the stage of reflex formation. 3. During temporary blocking of hypothalamic nuclei phasic changes arise in local SSCP, which was never observed after blocking the nonspecific thalamic nuclei. 4. During reversible blockade of subcortical structures synchronization of cortical and subcortical potentials is depressed first. Conditioned-reflex movements appear only when synchronization between cortex and subcortex is recovered. 5. The conclusion can be drawn from the results that the mammillary bodies play an important role in the formation of local SSCP at the beginning of DCR formation and that the nonspecific thalamic nuclei and the posterior hypothalamic nucleus are essential for this form of spatial synchronization to arise on stabilization of the reflex, when definite correlation is observed between the appearance of local, specific SSCP, realization of the reflex, and strengthening of synchronization between the cortex and subcortical formations.

Synthesis of 0-(2-0-α- d-glucopyranosyl)-β- d-galactopyranoside of optically pure δ-hydroxy-l-lysylglycine and -gd-hydroxy- l-lysylglycyl- l-glutamyl- l- aspartylglycine : Components of the glomerular basement membrane

The application of the levulinyl group as a temporary blocking group for the 2-OH function of galactose proved to be very efficient not only for the introduction of a β-linkage between galactose and the optically pure δ-hydroxy- l-lysylglycine, but also to link galactose, via an α-interglycosidic bond, with glucose. The partially protected glycodipeptide ( 7b) served as the starting product for the preparation of the naturally occuring glycopentapeptide ( 9b). The preparation of a conjugate between bovine serum albumin and the glycodipeptide ( 7c) will also be reported.

The hemodynamic component of compensation in the brain after unilateral blocking of the somatosensory cortex

In experiments on anesthetized and waking cats the dynamics of the cerebral blood flow was investigated by a thermoelectric method in one hemisphere during experimental injury to the somatosensory area of the opposite hemisphere. Temporary cold blocking of this area of the cortex gives rise to definite hemodynamic distorbances in the opposite hemisphere, namely a biphasic vascular response: an initial decrease in the blood supply followed by a long after-effect of an increase in the blood flow. Similar vascular responses also were observed after unilateral extirpation of the somatosensory cortex. Vascular responses of this type are evidence of increased activity of the cortical structures in the intact hemisphere and can be regarded as a compensatory response to local injury of particular areas of the cortex.

Evidence that intracellular and secreted light chains of a mouse IgG2 a plasmacytoma are monomers carrying a free thiol group

We have studied the intracellular light chains of Pl, a mouse plasmacytoma derived from ADJ PC5, which secreted IgG2 a and excess light chains, and its mutant X 2Pl which secreted only light chains. In both cases the intracellular light chains were not covalently dimerised, carrying, as did the freshly secreted light chains, one free thiol group per polypeptide chain. The presence of a free thiol group intracellularly indicates that temporary blocking cannot play a significant role in the control of assembly of the L chain into IgG2 a. The light chains excreted in the urine of mice carrying these plasmacytomas have blocked thiol groups, and these results show that such blocking must occur extracellularly after secretion.

Synthese des substances de groupe sanguin—IV : Synthese du 2-acetamido-2-desoxy-4- O-[2- O-(α- l-fucopyranosyl)-β- d-galactopyranosyl]- d-glucopyranose, porteur de la specificite H

The synthesis of a H blood group specific trisaccharide was performed by using benzyl ethers as temporary blocking groups for hydroxylic functions. Benzyl 2-acetamido-3,6-di- O-benzyl-2-deoxy-α- d- glucopyranoside was glycosylated by 3,4,6-tri- O-benzyl-1,2- O-benzyl-1,2- O-( tert-butoxyethylidene)-α- d-galactopyranose; after O-deacetylation, glycosylation by 2,3,4-tri- O-benzyl-α- l-fucopyranosyl bromide, and hydrogenolysis, 2-acetamido-2-deoxy-4- O-[2- O-(α- l-fucopyranosyl)-β- d-galactopyranosyl]- d-glucopyranose is obtained.

Corrections - Simple Alkanethiol Groups for Temporary Blocking of Sulfhydryl Groups of Enzymes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCorrections - Simple Alkanethiol Groups for Temporary Blocking of Sulfhydryl Groups of EnzymesDaniel Smith, Edward Maggio, and George KenyonCite this: Biochemistry 1975, 14, 14, 3292Publication Date (Print):July 15, 1975Publication History Published online12 November 2003Published inissue 15 July 1975https://doi.org/10.1021/bi00685a601RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (121 KB) Get e-Alerts Get e-Alerts

Simple alkanethiol groups for temporary blocking of sulfhydryl groups of enzymes

New reagents for the temporary blocking of active or accessible sulfhydryl groups of enzymes have been developed. These reagents, which are either alkyl alkanethiolsulfonates or alkoxycarbonylalkyl disulfides, rapidly and quantitatively place various RS- groups on the sulfhydryls to generate mixed disulfides. In all cases native enzymes can be regenerated with either dithiothreitol or beta-mercaptoethanol. In general the temporary blocking groups also afford total protection against normally inhibitory thiol blocking agents. When RS- groups were attached to rabbit muscle creatine kinase (EC 2.7.3.2), a trend toward lower residual activities with increasing bulk was observed. Treatment of the native creatine kinase with 14CH3HgC1 led to incorporation of greater than 1 equiv of CH3Hg- group per subunit. This CH3Hg- blocked enzyme was fully active, and the blocking group afforded no protection against iodoacetamide. These results suggest that CH3Hg- and the RS- groups are modifying two different sulhydryl groups on the enzyme. When papain (EC 3.4.4.10) was treated with excess methyl methanethiolsulfonate. complete and rapid inhibition was observed, and 1 equiv of CH3S- was incorporated/mol of active enzyme. Complete protection against normally inhibitory 5,5'-dithiobis(2-nitrobenzoic acid) was afforded by the temporary blocking group. When rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) was titrated with methyl methanethiolsulfonate, two sulfhydryl groups per subunit were found to be modified, one much more rapidly than the other. If one extrapolates the initial slope of the titration curve, the inactivation of the enzyme would be complete after modification of a single cysteinyl residue per subunit.

The role of the carotid chemoreceptors in the CO 2 -hyperpnea under hyperoxia.

In anesthetized rabbits rebreathing oxygen or inhaling constant mixtures of CO2 and O2, the influence of inactivation of the carotid sinus nerves by section or temporary cold blocking on the respiratory response to increased\(P_{A_{{\text{CO}}_{\text{2}} } } \) was investigated. In some of the experiments the vagi were intact, in others they were cut. Even during respiration of pure oxygen, in part of the animals blocking of the sinus nerves caused a slight diminution of ventilation which was significant only in the vagotomized preparation (average decrease by 11.4%). However, the diminishing effect of the blockade did not increase, but rather decreased, with increasing\(P_{A_{{\text{CO}}_{\text{2}} } } \). Similarly, section of the sinus nerves did not cause a significant shift or decrease of slope of the\(P_{A_{{\text{CO}}_{\text{2}} } } \) response curve. Evidently in the rabbit carotid chemoreceptors do not contribute essentially to the steady-state hyperpnea caused by hypercapnia under hyperoxic conditions.

Identity of the acetylcholine, adrenalin and serotonin receptors.

Interaction between two antagonistic mediators, acetylcholine and serotonin, was investigated by a kinetic method on the isolated ventricle ofMytilus grayanus andNeptunea sp. When both substances act simultaneously on the myocardium, they behave as antagonists of competitive and mixed types. Similar results were obtained on the isolated frog ventricle during simultaneous action of acetylcholine and adrenalin on the myocardium. Nonspecific factors inducing reversible denaturation of proteins (brief exposure to a high temperature or to 15% urea) led to temporary blocking of sensitivity to both mediators. After their action the sensitivity of the frog heart muscle to acetylcholine and adrenalin is gradually restored, and the recovery curves for the two mediators coincide. The identity of the receptor proteins for the antagonistic mediators is discussed.

Die Bedeutung der Afferenten, Verbo-Kinästhetischen Erregungen des Sprachapparates Für die Expressiven und Rezeptiven Sprachvorgänge bei Normalen und Sprachgestörten

Summary The author discusses results obtained with a method he developed to temporarily and mechanically exclude latent verbal motion (micromovements) in auditory comprehension of words and sentences, receptive reading and writing. The experiments were carried through with normal subjects and patients suffering from speech disturbance. By means of blowing hard into the mouth-piece of a glass-tube containing liquid, the subject is expected to raise this liquid to a given level within a fixed period of time. This method is superior to similar ones, through all muscle movement involved in speech and breathing processes connected therewith, being completely cut out. As a result of a series of experiments, the question as to whether receptive speech and thinking processes can occur despite complete temporary blocking of verbal-kinesthetic, afferent stimuli from the speech apparatus in normal and speech disturbed subjects (aphasics and deafmutes) can now be confirmed. In other words: normal subjects succeeded in comprehending words and sentences they heard and read while blowing into the tube, and they were able to repart them afterwards. The same applies to the aphasic, who within the limits of their receptive and expressive verbal capacity also showed positive results, despite the temporary blocking of their verbal-kinesthetic analyser, the function of which is of primary importance to these patients. Also experimental “deblocking” of disturbances in naming, repetition, and reading proved possible with aphasic patients, even under the increased difficulties of mechanically excluded, specific, latent, verbal motion. This means, that the participation of the verbal-kinesthetic analyser is not necessarily a precondition for the temporary restitution of certain verbal performances in aphasia. From this, the author concludes that despite the importance of verbalkinesthetic stimuli in the development of speaking and thinking processes, these neuromuscular, afferent stimuli (verbal-kinesthetic feedback) prove obsolete up to a degree, once the formation and storage of verbo-optical, verbo-auditive, and verbo-motor stereotypes (patterns, schemas) have reached a high degree of completion. Best proof for the justification of this assumption are the author's results obtained in experiments with a female subject suffering from congenital deafness, carried through with his blowing method. Additionally to her completely lacking the auditive analyser from birth, the function of the verbal-kinesthetic analyser, which played a dominant part in the development of her speech and thinking, was temporarily blocked. In this way, the auditive as well as the verbal-kinesthetic feedback were eliminated. Yet, the subject was still able to lip-read the words spoken to her by the experimentator while she was blowing, she understood their meaning, and could repart them afterwards; she was also able to read and comprehend texts shown to her while blowing. This shows that even with congenital deafness — provided an advanced stage of development has been reached in speech and thinking — the function of a single analyser (the optical analyser in this case) is sufficient to ensure various verbal and cognitive performances.

A Very Hard Reverberant Room

A 6000-cu ft reverberant room has been built as part of a new acoustic research facility. Interesting features are (1) a construction technique whereby uniform distribution of load on the resilient mounts was achieved without the use of temporary blocking, and (2) treatment of the walls to obtain low absorption and high damping. The finished room has a decay time of approximately 27 sec at 160 cps and it falls smoothly to 4 sec at 4000 cps. The transmission loss of the walls exceeds 60 db at 125 cps and appears to have no resonance dips. Construction details and performance data will be presented.

ARTERIO-VENOUS FISTULA OF CERVICAL REGION WITH REPEATED MASSIVE PHARYNGEAL HEMORRHAGE: REPORT OF A CASE

The authors reported a case of 46 yrs. old man, who had experienced repeated massive pharyngeal hemorrhage during the past twenty years. He had received X-ray radiation therapy under the diagnosisof pharyngeal angioma. However, according to the result of clinical investigations including arteriographicexamination, the authors was leading to the following diagnosis: unusual arterio-venous fistula arising from the deep tissue of the nasopharynx. For the purpose of controlling the recurrent hemorrhage, in the first step, the ligation of right external carotid artery was performed. But this procedurehad only a temporary effect and followed by the reapearance of massive hemorrhage.Therefore the authors decided to ligate the right common carotid artery. Before the ligation was performed, the patient had received the excercises to resist against the temporary blocking of the blood stream of common carotid artery with finger pressure. Electroencephalographies were made befor and after the blocking until no change occured by this procedure. After the ligation of right common carotid artery recurrent homorrhage was completely disappeared. The authors reviewed the literature of arterio-venous anastomosis and found that this was an especially unusual and interesting case.

MONETARY POLICY IN CONTINENTAL WESTERN EUROPE, 1944–52*

IN 1944-45 the monetary situations in Belgium, Denmark, France, Germany, Italy, and the Netherlands were strikingly similar. Each country had financed the war by printing notes, and the rigorous enforcement of price controls had kept price rises to relatively small proportions. Hence, these countries were faced with excess liquidity and repressed inflation. A reduction of the money supply was called for to prevent open inflation and to permit an orderly process of reconstruction. Belgium and Holland reduced excess liquidity through currency reforms, which consisted of the outright cancellation and temporary blocking of the money supply. They were thus spared from open inflation. France and Italy failed to reduce liquidity, and were consequently beset by a price-wage spiral. In Germany inflation was repressed to such an extent that money lost its normal functions and the economy lapsed into a state of barter. Three years elapsed before a currency reform eliminated excess liquidity and restored a credit economy. Only Denmark was able to avoid inflation without reducing the money supply, primarily because its excess liquidity was relatively small. The postwar reconstruction brought new inflationary pressures to all countries. Qualitative credit controls were generally a failure, unless accompanied by price and wage controls, and these were successful in curbing inflation only when supplemented by restrictive monetary or fiscal policies. By the end of 1948 production had reached prewar levels, and inflation had been arrested in all countries. A majority, however, still had deficits in their balance of payments. In countries such as Belgium, France, Germany, and Italy, which had relied primarily on monetary policy during the reconstruction, inflation was followed by a recession. No attempts were made to overcome the recession by expansionary monetary policy, because of the fear of renewed inflation and the persistent deficits in the balance of payments; the mere low-