Thermal And Structural Characterization of Commercial α-, β-, and γ-Cyclodextrins

α-, β-, and γ-cyclodextrins (CDs) marketed by five different companies were characterized from the thermal and structural point of view. Three αCD samples showed two-step DSC dehydration profiles and their XRD patterns were characteristic for αCD⋅6H₂O form I, whereas one brand with an apparent three-step DSC dehydration behaviour was a mixture of αCD⋅6H₂O form I and anhydrous αCD. The differences in the DSC profiles after dehydration and EGA onset decomposition temperatures recorded for the five βCD brands were attributed to different manufacturing and purification processes. The five γCDs brands showed a common thermal behaviour and very similar XRD patterns. The patterns did not match the idealized pattern of γCD⋅14.1H₂O, indicating the occurrence of two different hydrated crystal structures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Toward direct determination of conformations of protein building units from multidimensional NMR experiments. V. NMR chemical shielding analysis of N-formyl-serinamide,a model for polar side-chain containing peptides

Knowledge of chemical shift-structure relationships could greatly facilitate the NMR chemical shift assignment and structure refinement processes that occur during peptide/protein structure determination via NMR spectroscopy. To determine whether such correlations exist for polar side chain containing amino acid residues the serine dipeptide model, For-L-Ser-NH(2), was studied. Using the GIAO-RHF/6-31+G(d) and GIAO-RHF/TZ2P levels of theory the NMR chemical shifts of all hydrogen ((1)H(N), (1)H(alpha), (1)H(beta1), (1)H(beta2)), carbon ((13)C(alpha), (13)C(beta), (13)C') and nitrogen ((15)N) atoms have been computed for all 44 stable conformers of For-L-Ser-NH(2). An attempt was made to establish correlation between chemical shift of each nucleus and the major conformational variables (omega(0), phi, psi, omega(1), chi,(1) and chi(2)). At both levels of theory a linear correlation can be observed between (1)H(alpha)/phi, (13)C(alpha)/phi, and (13)C(alpha)/psi. These results indicate that the backbone and side-chain structures of For-L-Ser-NH(2) have a strong influence on its chemical shifts.     

The domain of partial attraction of a Poisson law

Groshev gave a characterization of the union of domains of partial attraction of all Poisson laws in 1941. His classical condition is expressed by the underlying distribution function and disguises the role of the mean of the attracting distribution. In the present paper we start out from results of the recent probabilistic approach and derive characterizations for any fixed >0 in terms of the underlying quantile function. The approach identifies the portion of the sample that contributes the limiting Poisson behavior of the sum, delineates the effect of extreme values, and leads to necessary and sufficient conditions all involving . It turns out that the limiting Poisson distributions arise in two qualitatively different ways depending upon whether >1 or <1. A concrete construction, illustrating all the results, also shows that in the boundary case when =1 both possibilities may occur.     

Thermal investigation of PEG 4000 — oxazepam binary system

A thermal study using DSC and Hot Stage Microscopy (HSM) was carried out to investigate the interaction in solid state of the binary system PEG 4000 — oxazepam, and to establish their phase diagram. The eutectic composition, which melting occurs at lower temperature as compared with the pure components, has been determined. The results obtained by DSC and HSM have indicated that PEG 4000 — oxazepam mixtures displays no obvious incompatibilities, and that the system shows a typical eutectic behaviour. However because of the closeness of the melting of PEG 4000 to the eutectic temperature, it was difficult to determine precisely the eutectic composition and temperature on the basis of DSC measurements alone. The use of heats of fusion corresponding to physical mixtures allowed an estimation of the eutectic composition at 6% w/w oxazepam. Additional information of temperature (57.6C) and composition (5–10% w/w oxazepam) of the eutectic was obtained by HSM using the contact method. This low melting temperature in this range of compositions offers advantages in terms of drug stability and easy manufacture.     

Anthracene Based Bulky Diol Hosts. Crystal Structures of a Free Host and of Inclusion Compounds with Dipolar Guests

X-ray crystal structures are reported of a free host compound 1, comprising two diphenylmethanol terminal groups attached to a central 9,10-ethynyl substituted anthracene unit, and of three inclusion compounds of a fluoren-9-ol substituted analogous host 2 with acetone, dimethyl sulphoxide (DMSO) and dimethylformamide (DMF) as guest, respectively. Despite the presence of two hydroxyl groups in 1, there is no O–H...O hydrogen bond between the molecules in the guest free crystal – only weaker C–H...O interactions and van der Waals' type connections. In the inclusion compounds of 2, H-bonded 1:2 host–guest associates are formed, where each of the host hydroxyl groups binds to a guest oxygen atom. The orientations of the host–guest connections in these complexes vary, being E for acetone and Z for both DMSO and DMF guests, relative to the host anthracene unit. The DMSO and DMF inclusion compounds of 2 proved to be isostructural.     

Bestimmung des tats?chlichen S?urechloridgehalts von Benzoylchlorid und Palmitoylchlorid

Zusammenfassung Zur Bestimmung des Säurechloridgehalts von Benzoyl- und Palmitoylchlorid wird ein Verfahren beschrieben, bei dem die zu untersuchende Probe in Gegenwart von eisessigsaurer Quecksilber(II)-acetatlösung mit einer Lösung von Morpholin in Tetrachlorkohlenstoff umgesetzt wird. Das Säurechlorid reagiert mit dem Morpholin unter Säureamidbildung. Der Überschuß der Morpholinbase wird mit HClO₄ in Gegenwart von Tropäolin 00 als Indicator zurücktitriert. Parallel wird eine Blindprobe durchgeführt. Säurechloride mit kürzeren Kohlenstoffketten lassen sich mit dieser Methode nicht bestimmen.     

Nuclear structure and chemical effects in internal conversion of the 35 keVM1+E2 transition in125Te

The relative conversion line intensities of the 35 keV transition in¹²⁵Te were measured using the 50 cm π√2 iron-yoke magnetic spectrometer. The transition was proved to be ofM1+(8.7±1.5)×10^?4 E2 multipolarity, the magnetic component being affected by the nuclear structure with λ=2.4±1.4. The conversion intensity ratio,0/N ₁ , was determined to be 0.115+0.005 for both Ag¹²⁵ I and Cu¹²⁵ I sources. It is in accordance with previous measurements for the Zn^125m Te and Pb^125m Te sources and differs from those for the^125mTeO₂ and Na₂H ₄ ^125m TeO₆ ones. The conversion coefficients were calculated for 32 configurations of the valence shell of free tellurium atom and ions and were compared with the experimental results.     

C(methyl)–H ⋅ ⋅ ⋅ π(aryl) Interaction Stabilizing Molecular Conformation. X-Ray Crystal Structure of an Inclusion Compound of a Nonprotic Host with Nitromethane Guest

In the cocrystal formation of a nonprotic polar (host) molecule (1) with nitromethane (guest) several weak, but directional, intermolecular interactions have vital importance. The endo conformation of the (N)-xylene group of the polycyclic succinimide-based host 1 is stabilized by a C_methyl $---$ H ??? π interaction [C ??? π /H ??? π distances are 3.554(7)/2.57 Å, the C $---$ H ??? π angle is 159^○], and the crystal packing is governed by dipole–dipole type interhost (C $ =$ )O ??? C( $ =$ O) connection [C ??? O $ =$ 3.000(5) Å and <C $ =$ O ??? C $ =$ 159.8(3)^○] in conjunction with possible C $---$ H ??? O interactions [with C ??? O distances ranging between 3.20 and 3.50 Å] involving the polar groups of both host and guest. Crystal data: 1 ??? nitromethane (1:1), C₂₆H₂₁O₂ N ? CH₃NO₂, M _w = 440.50, P2 ₁/n, a = 14.143(1), b = 7.973(1), c = 20.291(2) Å, β = 95.183(9)^○, Z = 4, D _c = 1.2840(2) g cm^?3, R = 0.055 for 1709 reflections.     

Every Moufang loop of odd order with nontrivial commutant has nontrivial center

We get a partial result for Phillips’ problem: does there exist a Moufang loop of odd order with trivial nucleus? First we show that a Moufang loop Q of odd order with nontrivial commutant has nontrivial nucleus, then, by using this result, we prove that the existence of a nontrivial commutant implies the existence of a nontrivial center in Q. Introducing the notion of commutantly nilpotence, we get that the commutantly nilpotence is equivalent to the centrally nilpotence for the Moufang loops of odd order.