Mirror symmetric broadband homodecoupled perfect echo spectroscopy

A new experiment for recording phase sensitive ω₁-broadband homodecoupled TOCSY spectra is presented. The method is an extension of the already existing perfect echo (PE) filter, proposed to sample t₁ chemical shift under sustained homodecoupling. The modification is made by attaching a time reversed perfect echo filter to a regular perfect echo scheme. Thus it becomes possible to acquire for longer t₁ acquisition times without compromising the quality of homodecoupling. The mirror symmetric double perfect echo is implemented into the evolution period of a TOCSY experiment. A spin lock pulse purges undesired dispersive antiphase components at the end of the central t₁ evolution period. Pure absorptive lineshapes with reduced proton spin multiplicities are obtained. The approach can be used in conjunction with real or constant time chemical shift evolution. In case of compounds with reduced T₂ relaxation time, the real time approach is advisable, where the echo delays are an extension of the t₁ evolution period. In this way, an unnecessary loss due to T₂ relaxation is avoided. Using the pulse sequence in constant time mode at high t_1max values gives ω₁-homodecoupled TOCSY spectra without a significant dependence of the transfer amplitude on J. All experiments were carried out using non uniform sampling to decrease the measurement time. Experimental setup, advantages and limitations are discussed.

An example of how to establish the thermodynamic stability relationship between two polymorphs of a compound highly prone to solvate formation

Upon transition from research to development, a new chemical entity, which acts upon the Kv1.5-potassium channel and blocks potassium flow in the atrium of the human heart, has been subjected to a crystallization screen. The sodium salt of an anthranilic acid amide with a heteroarylsulfonyl side chain forms solvates from all tested organic solvents. Solvent-free crystalline phases can only be obtained by drying certain solvates under suitable conditions. Two well crystalline solvent-free phases can be obtained this way. Three different methods were applied to determine their thermodynamic stability relationship from melting, solution and eutectic melting data. The different approaches are discussed and compared with respect to their accuracy and limitations.

The quaternary structure of insulin glargine and glulisine under formulation conditions

The quaternary structures of insulin glargine and glulisine under formulation conditions and upon dilution using placebo or water were investigated using synchrotron small-angle X-ray scattering. Our results revealed that insulin glulisine in Apidra® is predominantly hexameric in solution with significant fractions of dodecamers and monomers. Upon dilution with placebo, this equilibrium shifts towards monomers. Insulin glargine in Lantus® and Toujeo® is present in a stable hexamer/dimer equilibrium, which is hardly affected by dilution with water down to 1 mg/ml insulin concentration. The results provide exclusive insight into the quaternary structure and thus the association/dissociation properties of the two insulin analogues in marketed formulations.

The evolution of insulin glargine and its continuing contribution to diabetes care

The epoch-making discovery of insulin heralded a new dawn in the management of diabetes. However, the earliest, unmodified soluble insulin preparations were limited by their short duration of action, necessitating multiple daily injections. Initial attempts to protract the duration of action of insulin involved the use of various additives, including vasoconstrictor substances, which met with limited success. The subsequent elucidation of the chemical and three-dimensional structure of insulin and its chemical synthesis and biosynthesis allowed modification of the insulin molecule itself, resulting in insulin analogs that are designed to mimic normal endogenous insulin secretion during both fasting and prandial conditions. Insulin glargine was the first once-daily, long-acting insulin analog to be introduced into clinical practice more than 10 years ago and is specifically designed to provide basal insulin requirements. It has a prolonged duration of action and no distinct insulin peak, making it suitable for once-daily administration and reducing the risk of nocturnal hypoglycemia that is seen with intermediate-acting insulins. Insulin glargine can be used in combination with prandial insulin preparations and non-insulin anti-diabetic agents according to individual requirements.

Binding of phenol to R6 insulin hexamers

Small amounts of phenolic compounds are being used as preservatives in pharmaceutical insulin preparations. It has been shown previously that these compounds bind to specific sites on the insulin hexamer and act as allosteric effectors, inducing a transformation of the T6 hexamer to the R6 hexamer, via a T3R3 intermediate. In this article, the crystal structures of eight different insulin derivatives, all in the phenol-containing R6 form, are analyzed with respect to their phenol-binding sites. While six phenol molecules are normally bound per insulin hexamer, one of the engineered insulins appears to contain only three phenols but yet exists in an R6 conformation. This observation provides additional evidence for an inherent nonequivalence of the two trimers in the insulin hexamer. The unusual observation of a seventh phenol molecule bound to the hexamer of crystalline A21Gly-B31,B32Arg2 insulin (HOE 901), a long-acting derivative currently undergoing phase III clinical trials, provides a partial explanation for its protracted activity.

Structure of HOE/BAY 793 complexed to human immunodeficiency virus (HIV-1) protease in two different crystal forms--structure/function relationship and influence of crystal packing

Human immunodeficiency virus 1 (HIV-1) protease is a prime target in the search for drugs to combat the AIDS virus. The enzyme functions as a C2-symmetric dimer, cleaving the gag and gag-pol viral polyproteins at distinct sites. The possession of a twofold axis passing through the active site, has led to the design of C2-symmetrical inhibitors in the form of substrate-based transition-state analogs. One of the most active compounds of this class of inhibitors is HOE/BAY 793, which contains a vicinal diol central unit [Budt, K.-H., Hansen, J., Knolle, J., Meichsner, C., Paessens, A., Ruppert, D. & Stowasser, B. & Winkler, I. (1990) European Patent application EP0428,849; Budt, K.-H., Hansen, J., Knolle, J., Meichsner, C., Ruppert, D., Paessens, A. & Stowasser B. (1993) IXth International Conference on AIDS; Budt, K.-H., Peyman, A., Hansen, J., Knolle, J., Meichsner, C., Paessens, A., Ruppert, D. & Stowasser, B. (1995) Bioorg. Med. Chem. 3, 559-571.] The structure of this inhibitor bound to HIV-1 protease, in two different crystal forms, has been solved at 0.24-nm resolution using X-ray crystallography. In both forms, the details of the inhibitor-protease interactions revealed an overall asymmetric binding mode, especially between the central diol unit and the active-site aspartates. The main binding interactions comprise several specific H-bonds and hydrophobic contacts, which rationalize many of the characteristics of the structure/activity relationship in the class of vicinal diol inhibitors. In a general analysis of the mobility of the flap regions, which cover the active site and participate directly in binding, using our structures and the HIV protease models present in the Brookhaven databank, we found that in most structures the flexibility of the flaps is limited by local crystal contacts. However, in one of the structures presented here, no significant crystal contacts to the flap regions were present, and as a result the flexibility of the inhibitor bound flaps increased significantly. This suggests that the mobility and conformational flexibility of the flap residues are important in the functioning of HIV-1 protease, and must be considered in the future design of drugs against HIV protease and in structure-based drug design in general.

Crystal structure of active elongation factor Tu reveals major domain rearrangements

The crystal structure of intact elongation factor Tu (EF-Tu) from Thermus thermophilus has been determined and refined at an effective resolution of 1.7 A, with incorporation of data extending to 1.45 A. The effector region, including interaction sites for the ribosome and for transfer RNA, is well defined. Molecular mechanisms are proposed for transduction and amplification of the signal induced by GTP binding as well as for the intrinsic and effector-enhanced GTPase activity of EF-Tu. Comparison of the structure with that of EF-Tu-GDP reveals major mutual rearrangements of the three domains of the molecule.

Crystals of intact elongation factor Tu from Thermus thermophilus diffracting to high resolution

The intact elongation factor Tu from the extreme thermophile Thermus thermophilus has been crystallized as a complex with the GTP analogue guanosine-5'-(beta,gamma-imido)triphosphate. The crystals are very stable in the X-ray beam and diffract to 1.9 A resolution. They exhibit space group C2, with a = 150.3(6) A, b = 99.6(3) A, c = 40.1(1) A, beta = 95.4(2) degrees, and contain one elongation factor Tu molecule per asymmetric unit.

Thrombocytopenic episodes in patients with well-functioning renal allografts. Inverse relationship between platelet count and platelet size pointing to intermittent platelet destruction

20 out of 50 patients with well-funcioning renal allograft displayed at least one platelet count below 110 X 10(9)/1 (mean -2 SD of controls). For estimation of platelet production during thrombocytopenic episodes, the percentage of large platelets in the peripheral blood was determined which revealed an inverse relationship (p less than 0.01) to the platelet count, indicating that these thrombocytopenias were due to increased platelet consumption. Immunosuppressive treatment as well as rejection processes could be excluded as major pathogenetic factors whereas anti-platelet autoantibodies may contribute to this phenomenon.

[Oral health for everyone--an unattainable goal? Analysis of a questionnaire among 1200 Swiss recruits]

The attitude of 1085 Swiss military recruits towards the dentist and dental care, their knowledge of periodontal disease and its prevention, the incidence of smoking and the frequency of eating sweets as well as interest in their own teeth in general was determined by use of a questionnaire. The results showed a positive attitude on the part of the participants towards their own teeth and a definite motivation for good oral health. The oral hygiene habits of only a minority could be classified as sufficient, the knowledge of periodontal disease and its prevention were limited. Smoking and eating sweets were found to be widespread. It can be stated, therfore, that hygiene instruction for improvement of oral health by the dental profession as well as motivational efforts towards general health education at home and at school were unfortunately unsatisfactory.

Gingivitis in Zurich schoolchildren. A reexamination after 20 years

In 1957 the periodontal health of 1350 Zurich schoolchildren was assessed. The same investigator (M.Z.) examined 1217 children in the same school district 18 years later. 909 children were considered for statistical analysis. Only 9.1% were found to be free from gingival inflammation. 32% of the papillary and marginal gingival areas showed inflammatory signs. Prevalence of gingivitis was similar in different socioeconomic groups and in children treated by general practitioners and school dental clinics respectively. Gingivitis prevalence was remarkably similar in 1957 and 1975. An increase in the intensity of inflammation was, however, statistically significant. Reconsideration and modification of the existing measures in preventive periodontology are indicated.