Analysis of ergonomics problems contact-centers

The analysis of the ergonomic problems of the contact center. It allocates main factors of influence on man- operator

An <i>n</i>→π* Interaction in Aspirin: Implications for Structure and Reactivity

Stereoelectronic effects modulate molecular structure, reactivity, and conformation. We find that the interaction between the ester and carboxyl moieties of aspirin has a previously unappreciated quantum mechanical character that arises from the delocalization of an electron pair (n) of a donor group into the antibonding orbital (π*) of an acceptor group. This interaction affects the physicochemical attributes of aspirin and could have implications for its pharmacology

Intimate Interactions with Carbonyl Groups: Dipole–Dipole or <i>n</i>→π*?

Amide carbonyl groups in proteins can engage in CO···CO and C–X···CO interactions, where X is a halogen. The putative involvement of four poles suggests that these interactions are primarily dipolar. Our survey of crystal structures with a C–X···CO contact that is short (i.e., within the sum of the X and C van der Waals radii) revealed no preferred C–X···CO dihedral angle. Moreover, we found that structures with a short X^–···CO contact display the signatures of an <i>n</i>→π* interaction. We conclude that intimate interactions with carbonyl groups do not require a dipole

<i>n</i>→π* Interactions Engender Chirality in Carbonyl Groups

An <i>n</i>→π* interaction stems from the delocalization of the electron pair (<i>n</i>) of a donor group into the antibonding orbital (π*) of a carbonyl group. Crystallographic analyses of five pairs of diastereoisomers demonstrate that an <i>n</i>→π* interaction can induce chirality in an otherwise planar, prochiral carbonyl group. Thus, a subtle delocalization of electrons can have stereochemical consequences

<i>n</i>→π* Interactions Engender Chirality in Carbonyl Groups

An <i>n</i>→π* interaction stems from the delocalization of the electron pair (<i>n</i>) of a donor group into the antibonding orbital (π*) of a carbonyl group. Crystallographic analyses of five pairs of diastereoisomers demonstrate that an <i>n</i>→π* interaction can induce chirality in an otherwise planar, prochiral carbonyl group. Thus, a subtle delocalization of electrons can have stereochemical consequences

<i>n</i> → π* Interaction and <i>n</i>)(π Pauli Repulsion Are Antagonistic for Protein Stability

n → π* Interaction and n)(π Pauli Repulsion Are Antagonistic for Protein Stabilit

Effect of thiamethoxam on the survival of brood in <i>Apis mellifera</i> L. colonies placed in mustard fields

Honey bees come under stress if thiamethoxam (a neonicotinoid insecticide) is used on their forage crops. The lethal and sub-lethal effects of this insecticide have largely been documented on foraging bees in comparison to the non-foraging stages especially the immature stages. Hence, the present study, to know the effect of thiamethoxam (25 and 50 g a.i. ha−1) on the brood of Apis mellifera colonies in mustard was conducted. Brood index, compensation index, and brood termination rate were calculated for the brood area (2 sq. inch) selected at two time intervals i.e. at the time of spray (D0) and seven days after that (D7). Brood index for the brood selected at D7 of thiamethoxam applied at 25 g a.i. ha−1 was statistically at par with the untreated control i.e. its value at 21 days (1.00 ± 0.00-4.48 ± 0.04) was statistically at par with the untreated control (1.00 ± 0.00-4.66 ± 0.01). However, in other treatments viz. brood selected at D0 in thiamethoxam applied at 25 g a.i. ha−1 and at D0 and D7 in thiamethoxam applied at 50 g a.i. ha−1, significant brood mortality was recorded at the end of the brood cycle. Compensation indices and brood termination rates also showed similar effects. Overall, it is concluded that thiamethoxam at the recommended dose i.e. 25 g a.i. ha−1 did not affect the brood which was reared 7 days after the application.</p

Nature of Amide Carbonyl−Carbonyl Interactions in Proteins

Nature of Amide Carbonyl−Carbonyl Interactions in Protein

The Aberrance of the 4<i>S</i> Diastereomer of 4-Hydroxyproline

Prolyl 4-hydroxylases install a hydroxyl group in the 4R configuration on the γ-carbon atom of certain (2S)-proline (Pro) residues in tropocollagen, elastin, and other proteins to form (2S,4R)-4-hydroxyproline (Hyp). The gauche effect arising from this prevalent post-translational modification enforces a Cγ-exo ring pucker and stabilizes the collagen triple helix. The Hyp diastereomer (2S,4S)-4-hydroxyproline (hyp) has not been observed in a protein, despite the ability of electronegative 4S substituents to enforce the more common Cγ-endo ring pucker of Pro. Here, we use density functional theory, spectroscopy, crystallography, and calorimetry to explore the consequences of hyp incorporation on protein stability using a collagen model system. We find that the 4S-hydroxylation of Pro to form hyp does indeed enforce a Cγ-endo ring pucker but a transannular hydrogen bond between the hydroxyl moiety and the carbonyl of hyp distorts the main-chain torsion angles that typically accompany a Cγ-endo ring pucker. This same transannular hydrogen bond enhances an n→π* interaction that stabilizes the trans conformation of the peptide bond preceding hyp, endowing hyp with the unusual combination of a Cγ-endo ring pucker and high trans/cis ratio. O-Methylation of hyp to form (2S,4S)-4-methoxyproline (mop) eliminates the transannular hydrogen bond and restores a prototypical Cγ-endo pucker. mop residues endow the collagen triple helix with much more conformational stability than do hyp residues. These findings highlight the critical importance of the configuration of the hydroxyl group installed on Cγ of proline residues

Prolyl 4‑Hydroxylase: Substrate Isosteres in Which an (<i>E</i>)- or (<i>Z</i>)‑Alkene Replaces the Prolyl Peptide Bond

Collagen prolyl 4-hydroxylases (CP4Hs) catalyze a prevalent posttranslational modification, the hydroxylation of (2S)-proline residues in protocollagen strands. The ensuing (2S,4R)-4-hydroxyproline residues are necessary for the conformational stability of the collagen triple helix. Prolyl peptide bonds isomerize between cis and trans isomers, and the preference of the enzyme is unknown. We synthesized alkene isosteres of the cis and trans isomers to probe the conformational preferences of human CP4H1. We discovered that the presence of a prolyl peptide bond is necessary for catalysis. The cis isostere is, however, an inhibitor with a potency greater than that of the trans isostere, suggesting that the cis conformation of a prolyl peptide bond is recognized preferentially. Comparative studies with a Chlamydomonas reinhardtii P4H, which has a similar catalytic domain but lacks an N-terminal substrate-binding domain, showed a similar preference for the cis isostere. These findings support the hypothesis that the catalytic domain of CP4Hs recognizes the cis conformation of the prolyl peptide bond and inform the use of alkenes as isosteres for peptide bonds