scholarly journals The role of an active site Mg2+ in HDV ribozyme self-cleavage: insights from QM/MM calculations

2015 ◽  
Vol 17 (1) ◽  
pp. 670-679 ◽  
Author(s):  
Vojtěch Mlýnský ◽  
Nils G. Walter ◽  
Jiří Šponer ◽  
Michal Otyepka ◽  
Pavel Banáš
Keyword(s):  
Active Site ◽  
The Self ◽  
Direct Impact ◽  
Cleavage Reaction ◽  
Hdv Ribozyme ◽  
Specific Position

The specific position and coordination of active site Mg2+ ion have a significant direct impact on the self-cleavage reaction in HDV ribozyme.

scholarly journals An analysis of the role of active site protic residues of cytochrome P-450s: mechanistic and mutational studies on 17α-hydroxylase-17,20-lyase (P-45017α also CYP17)

1998 ◽  
Vol 330 (2) ◽  
pp. 967-974 ◽  
Author(s):  
Peter LEE-ROBICHAUD ◽  
E. Monika AKHTAR ◽  
Muhammad AKHTAR
Keyword(s):  
Hydrogen Bonds ◽  
Active Site ◽  
Catalytic Properties ◽  
Active Form ◽  
Proton Donor ◽  
Wild Type ◽  
Cleavage Reaction ◽  
Acyl Carbon ◽  
Hydroxylation Reaction

Certain cytochrome P-450s involved in the transformation of steroids catalyse not only the hydroxylation process associated with the group of enzymes, but also an acyl-carbon cleavage reaction. The hydroxylation occurs using an iron-monooxygen species while the acyl-carbon cleavage has been suggested to be promoted by an iron peroxide. In this paper we have studied the role of active site protic residues, Glu305 and Thr306, in modulating the two activities. For this purpose, the kinetic parameters for the hydroxylation reaction (pregnenolone → 17α-hydroxypregnenolone) and two different versions of acyl-carbon cleavage (17α-hydroxypregnenolone → dehydroepiandrosterone and 3β-hydroxyandrost-5-ene-17β-carbaldehyde → 3β-hydroxyandrost-5,16-diene+androst-5-ene-3β,17α-diol) were determined using the wild-type human CYP17 and its eight different single and double mutants. In addition the propensity of the proteins to undergo a subtle rearrangement converting the 450 nm active-form into an inactive counterpart absorbing at 420 nm, was monitored by measuring the of the P-450 → P-420 conversion. The results are interpreted to draw the following conclusions. The functional groups of Glu305 and Thr306 do not directly participate in the two proton delivery steps required for hydroxylation but may be important participants for the provision of a net work of hydrogen bonds for ‘activating’ water that then acts as a proton donor. The loss of any one of these residues is, therefore, only partially debilitating. That the mutation of Thr306 impairs the hydroxylation reaction more than it does the acyl-carbon cleavage is consistent with the detailed mechanistic scheme considered in this paper. Furthermore attention is drawn to the fact that the mutation of Glu305 and Thr306 subtly perturbed the architecture of the active site, which affects the geometry of this region of the protein and therefore its catalytic properties.

The role of the self in creative expression

2014 ◽  
Author(s):  
Kristin Donnelly ◽  
Radmila Prislin ◽  
Ryan Nicholls
Keyword(s):  
Creative Expression ◽  
The Self

The role of the self in organizational justice

2007 ◽  
Author(s):  
D. Ramona Bobocel ◽  
Russell E. Johnson ◽  
Joel Brockner
Keyword(s):  
Organizational Justice ◽  
The Self

The role of egocentrism in estimating social evaluations of the self

2004 ◽  
Author(s):  
John Chambers ◽  
Nick Epley ◽  
Paul Windschitl
Keyword(s):  
The Self

From Container to Claustrum: Projective Identification in Couples

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Tamara Feldman
Keyword(s):  
Psychological Health ◽  
Projective Identification ◽  
The Self ◽  
The Other ◽  
Intimate Partners ◽  
And Control ◽  
The Relationship ◽  
As If

This paper is a contribution to the growing literature on the role of projective identification in understanding couples' dynamics. Projective identification as a defence is well suited to couples, as intimate partners provide an ideal location to deposit unwanted parts of the self. This paper illustrates how projective identification functions differently depending on the psychological health of the couple. It elucidates how healthier couples use projective identification more as a form of communication, whereas disturbed couples are inclined to employ it to invade and control the other, as captured by Meltzer's concept of "intrusive identification". These different uses of projective identification affect couples' capacities to provide what Bion called "containment". In disturbed couples, partners serve as what Meltzer termed "claustrums" whereby projections are not contained, but imprisoned or entombed in the other. Applying the concept of claustrum helps illuminate common feelings these couples express, such as feeling suffocated, stifled, trapped, held hostage, or feeling as if the relationship is killing them. Finally, this paper presents treatment challenges in working with more disturbed couples.

Cartesian Fingerprints in Beckett's Imagination Dead Imagine

2012 ◽  
Vol 21 (2) ◽  
pp. 223-243
Author(s):  
Irit Degani-Raz
Keyword(s):  
The Self ◽  
Levels Of Abstraction ◽  
The Media ◽  
The Mind ◽  
Limiting Case

The idea that Beckett investigates in his works the limits of the media he uses has been widely discussed. In this article I examine the fiction Imagination Dead Imagine as a limiting case in Beckett's exploration of limits at large and the limits of the media he uses in particular. Imagination Dead Imagine is shown to be the self-reflexive act of an artist who imaginatively explores the limits of that ultimate medium – the artist's imagination itself. My central aim is to show that various types of structural homologies (at several levels of abstraction) can be discerned between this poetic exploration of the limits of imagination and Cartesian thought. The homologies indicated here transcend what might be termed as ‘Cartesian typical topics’ (such as the mind-body dualism, the cogito, rationalism versus empiricism, etc.). The most important homologies that are indicated here are those existing between the role of imagination in Descartes' thought - an issue that until only a few decades ago was quite neglected, even by Cartesian scholars - and Beckett's perception of imagination. I suggest the use of these homologies as a tool for tracing possible sources of inspiration for Beckett's Imagination Dead Imagine.

Samuel Beckett's Disruptive Translations of ‘je voudrais que mon amour meure’

2019 ◽  
Vol 28 (2) ◽  
pp. 163-178
Author(s):  
Trask Roberts
Keyword(s):  
Samuel Beckett ◽  
The Self ◽  
Irish Poetry ◽  
Poetic Translation

Self-translators are often granted freedoms in their translations unimaginable for standard translators. Whereas a standard translation usually prizes sameness (or invisibility as Lawrence Venuti argues), the self-translator may instead highlight difference or disruption. A burgeoning subfield of criticism has outlined the ways in which one of the most famous of these self-translators, Samuel Beckett, makes use of his role as translator to further the reach of his work beyond the constraints of a monolingual text. Whereas most of this criticism has taken aim at Beckett's prose and theater, this essay asks what can be gleaned about Beckett's translation style from his early poetry. Here I focus on Beckett's four-line, untitled poem which begins ‘je voudrais que mon amour meure’ (‘I would like my love to die’). Originally published in 1948 in the bilingual journal Transition Forty-eight, this poem would go on to be edited, translated, reedited, and retranslated over the course of nearly thirty years. The various iterations and translations of the poem are not always harmonious and instead force the reader to consider more deeply the themes of the poem and to question the role of translation. I read the poem in light of Beckett's 1934 essay ‘Recent Irish Poetry’ as well as consider it in response to W.B. Yeats' 1899 poem ‘He Wishes His Beloved Were Dead’. By situating the poem in this context, I argue that this poem is a manifestation of Beckett's argument in the essay that poetry must take into account the division between poet and object. His short poem demonstrates this division as well as that between original and translation and thus allows us a window onto his translation project at large. Considering Beckett's poetic translation permits us to consider how a complementarity of intention towards language does not necessarily entail complementary translations.

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