Probing the molecular and electronic structure of capsaicin: a spectroscopic and quantum mechanical study.

The conformational preferences of capsaicin were investigated by using the hybrid meta density functional theory (DFT) method MPWB1K. Its flexible, pendant side chain allows for a multitude of conformations only slightly different in energy. The distinctive vibrational features of the most stable conformers were characterized. To elucidate the most favorable reaction sites of capsaicin for radical scavenging, various homolytic bond-dissociation energies were also calculated. Of the possible radical intermediates, the allyl and benzyl radicals are energetically preferred. The filled and empty electronic structures of capsaicin were investigated by exploiting the photoelectron and electron-transmission spectra also of reference molecules and suitable quantum-mechanical calculations. On this basis, a reliable pattern of the vertical ionization energies and electron-attachment energies of capsaicin was proposed. The frontier pi molecular orbitals are concentrated over the vanillyl moiety, with a modest influence of the amidic-aliphatic chain. The (negative) first vertical electron affinity is predicted to be similar to that of benzene. The absorption spectrum of capsaicin and its change by conversion into a phenolic deprotonated anion (modest bathochromic displacement) or a phenoxyl neutral radical (from colorless to red) were interpreted with time-dependent DFT calculations. ESR measurements following chemical or electrochemical reduction of capsaicin did not lead to detection of the corresponding radical anion. The spectra show fragmentation of the original molecule and formation of a variety of radical species which are believed to have a semiquinonic structure.

Spectroscopic and theoretical study of the electronic structure of curcumin and related fragment molecules.

The low volatility and thermal instability made the photoelectron (PE), electron transmission (ET), and dissociative electron attachment (DEA) spectroscopy measurements on curcumin (a potent chemopreventive agent) unsuccessful. The filled and empty electronic structure of curcumin was therefore investigated by exploiting the PES, ETS, and DEAS results for representative fragment molecules and suitable quantum-mechanical calculations. On this basis, a reliable pattern of the vertical ionization energies and electron attachment energies of curcumin was proposed. The pi frontier molecular orbitals (MOs) are characterized by sizable interaction between the two phenol rings transmitted through the dicarbonyl chain and associated with a remarkably low ionization energy and a negative electron attachment energy (i.e., a largely positive electron affinity), diagnostic of a stable anion state not observable in ETS. The lowest energy electronic transitions of half-curcumin and curcumin and their color change by alkalization were interpreted with time-dependent density functional theory (DFT) calculations. For curcumin, it is shown that loss of a phenolic proton occurs in alkaline ethanolic solution.

Theoretical study of the structure and bonding in bridgehead diphosphines.

The molecular structures of a representative selection of medium-sized bicyclic diphosphines (i.e., diphosphanes) were studied by means of the ab initio second-order Møller-Plesset (MP2) method. The calculated results matched the available X-ray crystallographic data reasonably. A distinctive structural aspect is that all the 1,5-diphosphabicyclo[3.3.3]undecane systems, the 1,6-diphosphabicyclo[4.4.4]tetradecane free base, and its axially disubstituted derivatives adopt the out,out-conformation, whereas the monosubstituted [4.4.4] species prefer the out,in-arrangement. The intrabridgehead interaction was described in terms of polarity, bond order index, force constant, vibrational frequency, and nature of the critical point of the total electron density. The electronic structures of the [3.3.3] and [4.4.4] diphosphanes were theoretically investigated by means of their NMR spectroscopic properties. The chemical shifts and indirect nuclear spin-spin coupling constants, computed by density functional theory (DFT)-based methods, were in satisfactory agreement with the experimental values. In particular, the theoretical results yielded a consistent account of the strong orientational effects of the phosphorus lone pair and coordination on delta((31)P), J((31)P-(31)P), and J((31)P-C) that show remarkable changes of sign and magnitude within this class of compounds.

Social Security: a financial appraisal for the median voter.

Several explanations have been proposed for why voters continue to support unfunded social security systems. Browning (1975) suggests that the extremely large unfunded pension systems of most democracies depend on the existence of a voting majority composed of middle-aged and older people who fail to fully internalize the cost of financing the system. In fact, when voting, economically rational workers consider only their current and future contributions to the system and their expected pension benefits--not their past contributions, which they regard as sunk costs. If, for a majority of voters, the expected continuation return from social security exceeds the return from alternative assets, an unfunded social security system is politically sustainable. This article explores the validity of Browning's proposition by quantifying the returns that U.S. voters in presidential elections from 1964 to 1996 have obtained, or expect to obtain, from Social Security. Did "investments" in Social Security outperform alternative forms of investment, such as mutual funds or pension funds, for a majority of the voters? What can be expected for the future? The U.S. Social Security system redistributes income within age cohorts on the basis of sex, income, and marital status. To account for some of these features, the median voter is represented by a family unit whose members--a husband who accounts for 70 percent of household earnings and a wife who accounts for 30 percent--make joint economic and voting decisions. Thus, retirement and survival benefits paid out to the spouse of an insured worker can be included in the calculation of Social Security returns. Interval estimates of voters' family incomes from the U.S. Census Bureau were used to obtain the median voter's household earnings. The median voter's age is derived from the ages of those who voted in presidential elections, not from the ages of the entire electorate. The median voter's contributions to Social Security are the product of the joint employer/employee Old-Age and Survivors Insurance (OASI) tax rate and employee earnings. Data on actual contributions are available for median voters in the 1964 to 1976 elections; Social Security Administration (SSA) estimates are used for future tax rates and average wage growth rates. Data on actual old-age, retirement, and survivor benefits, as well as estimates of future benefits, are also available from SSA. Analysis of ex-post returns from "investing" in Social Security and from a buy-and-hold strategy applied to three alternative assets--the Standard & Poor's Composite Index (S&P), the Dow Jones Industrial Average (DJIA), and U.S. government bonds--shows surprising results. In 1964 and 1968, Social Security largely outperformed the other three assets. In 1972, Social Security and the stock market performed almost equally. In 1976, however, the median voter would have been better off in the stock market. The expected returns for median voters in later elections cannot be directly compared with realized returns from alternative assets. However, estimates range from 5.7 percent in 1984 to 7.0 percent in 1996 and thus compare favorably with average returns of 5.6 percent for S&P, 5.3 percent for DJIA, and 2.1 percent for government bonds over the 1964-1996 period. Although these findings must be taken with caution since they compare ex-post returns, they show that, despite a continuous reduction in profitability, Social Security still represents a safe, high-return asset for a majority of families.

[Residual gastric mucosa after gastrectomy: development of precancerous lesions]. / Mucosa gastrica residua a gastroresezione: dinamica delle lesioni precorritrici del carcinoma.

The gastric remnant can be regarded as a model to investigate the events of gastric carcinogenesis of intestinal type. Histologic changes precursor of the malignancy develop in higher incidence in the postoperative stomachs than in non-resected ones. 316 patients hemi-gastrectomized for peptic ulcer were assessed by an endoscopic-histologic study to provide further informations on the sequential chain of histologic lesions that precede the development of cancer. The anastomosis was by far the commonest diseased area at endoscopy, particularly in the patients with a Billroth II resection (p < 0.0004). The 10% of the 233 patients biopsied evidenced a normal gastric mucosa, in the others Superficial Gastritis 74%, Chronic Atrophic Gastritis 36%, Cystic Dilatation 52%, Foveolar Hyperplasia 29%, Intestinal Metaplasia 39%, moderate-severe Dysplasia 6% as single abnormality or variously associated were observed. The stoma was the most damaged area at histology. The occurrence of the DC, the FI and the IM at the anastomotic site was significative (p values between 0.02 and 0.001). The earliest postoperative histologic lesion was the CAG, evidenced, in mean 13 years after operation, the latest the DC observed in mean 18 years after surgery (p < 0.004). The IM, the IF, the CD, and the dysplasia in association with the CAG were observed at postoperative intervals shorter when non-associated with CAG (respective p value: NS, < 0.03, < 0.0002, NS). The probability of transition from an histologic lesions to a more advanced one in our patients was similar to that of a non resected population at medium--high risk of gastric cancer.

[Osteopetrosis and renal acidosis: a new case of this rare syndrome]. / Osteopetrosi ed acidosi renale: un nuovo caso di questa rara sindrome.

The association between osteopetrosis and renal acidosis is not accidental, but represents a well-known syndrome with autosomal recessive transmission, due to carbonic anhydrase II(CA II) deficiency. The disease is extremely rare (only few reports in the literature). The diagnosis is confirmed by CA II erythrocyte assay. However, this finding is not essential when the clinical picture is complete, as in the case reported in this paper, which presents a patient with osteopetrosis, proximal tubular acidosis, intracranial calcifications, psychomotor retardation and short stature. Prenatal diagnosis will rely on the genetic study of DNA by molecular probes, since it is already well-known that the coding gene for CA II is on the long arm of chromosome 8 (8q22).