[A case of hemolysis and acute kidney disease caused by rectal damage due to glycerin enema].

A male patient in his sixties with a long-term history of schizophrenia had been received glycerin enema once or twice a week in a mental hospital. He was emergently transferred to our hospital due to fever, vomiting, hematuria, and dyspnea. Laboratory findings on admission showed an elevation of white blood cells indicating inflammation, hemolysis, and renal dysfunction. Plain CT showed pleural effusion and ascites, elevated levels of perirectal fat, in addition to extraintestinal gas. Based on these findings, he was diagnosed with rectal damage caused by the glycerin enema and associated hemolysis with acute renal failure. He was kept under conditions of nil by mouth and received intravenous antibiotics, diuretic drug, and haptoglobin. Eventually, his condition improved with these conservative therapies. In this case, it is assumed that the hemolysis was caused by the influx of glycerin in the cytoplasm and an increase of osmotic pressure. Care should be taken during glycerin enema, which is widely used in daily practice as well as in home care settings.

The structure of metallo-DNA with consecutive thymine-HgII-thymine base pairs explains positive entropy for the metallo base pair formation.

We have determined the three-dimensional (3D) structure of DNA duplex that includes tandem Hg(II)-mediated T-T base pairs (thymine-Hg(II)-thymine, T-Hg(II)-T) with NMR spectroscopy in solution. This is the first 3D structure of metallo-DNA (covalently metallated DNA) composed exclusively of 'NATURAL' bases. The T-Hg(II)-T base pairs whose chemical structure was determined with the (15)N NMR spectroscopy were well accommodated in a B-form double helix, mimicking normal Watson-Crick base pairs. The Hg atoms aligned along DNA helical axis were shielded from the bulk water. The complete dehydration of Hg atoms inside DNA explained the positive reaction entropy (ΔS) for the T-Hg(II)-T base pair formation. The positive ΔS value arises owing to the Hg(II) dehydration, which was approved with the 3D structure. The 3D structure explained extraordinary affinity of thymine towards Hg(II) and revealed arrangement of T-Hg(II)-T base pairs in metallo-DNA.

Specific interactions between silver(I) ions and cytosine-cytosine pairs in DNA duplexes.

Very specific binding of the Ag(i) ion unexpectedly stabilized DNA duplexes containing the naturally occurring cytosine-cytosine (C-C) mismatch-base pair; because the C-C pair selectively binds to the Ag(i) ion, we developed a DNA-based Ag(i) sensor that employed an oligodeoxyribonucleotide containing C-C pairs used for Ag(i) binding sites.

Structural and physicochemical features on the metal-mediated base pairs.

The chemical structure of the mercury-mediated T-T pair (T-Hg(I)I-T) was determined with (15)N NMR spectroscopy. In order to determine the chemical structure of the T-Hg(I)I-T pair, (15)N-(15)N J-coupling across a metal center (2JNN) was employed. Notably, this is the first observation of (2)J(NN) in a biological macromolecule (DNA duplex). This pairing mode was found to be a irregular metal ion-binding mode for DNA and RNA molecules, in which imino proton-metal exchange processes are included. Accordingly, (2)J(NN) is highly important for the determination of the chemical structures of metal-mediated base pairs.

Structural analyses on the mercuryII-mediated T-T base pair.

Recently, it was reported that T-T mismatches can specifically recognize Hg(II), and form T-Hg(II)-T pairs. In order to understand the structure and properties of the T-Hg(II)-T pair, we measured NMR spectra for a DNA duplex, d(CGCGTTGTCC) x d(GGACTTCGCG), with two successive T-T mismatches (Hg(II)-binding sites) in the middle of the duplex. We identified imino proton resonances of the T-T mismatches in mercury-free duplex, and performed titration experiments with Hg(II) by using 1-dimensional (1D) (1)H NMR spectra. From the titration spectra, disappearances of imino proton signals were observed upon the addition of Hg(II). Furthermore, we observed additional signals of transient species, most likely mono-mercurated duplexes. This is an evidence that structural transformations between Hg(II)-free and Hg(II)-bound forms are slow enough for each species to give independent signals. These data strongly suggest that the imino protons of thymine bases were substituted with Hg(II), to form T-Hg(II)-T pairs in which one Hg(II) cross-links two N3 atoms of thymines.

Spectroscopic analysis of AgI-DNA complex.

It has recently been reported that C-C mismatches were able to recognize Ag(I) specifically, and form Ag(I)-mediated cytosine-cytosine base pairs (C-Ag(I)-C pair). In this study, we explored DNA sequences, which are appropriate for structural studies of this new type of metal-mediated base pairs. For this experiments, we synthesized four kinds of DNA duplexes including a single C-C mismatch. By using UV spectra, we performed titration experiments of DNA duplexes with AgNO(3). Within the sequences we tested, it was found that the DNA duplex: 5'-CGCGCGTCC-3' x 5'-GGACCCGCG-3' showed 1:1 complexation of this DNA duplex and Ag(I). In addition, a DNA duplex: 5'-TAAATCTAATA-3' x 5'-TATTACATTTA-3' also exhibited a similar character. Therefore, these two DNA duplexes are interesting candidates for structural analyses.

NMR spectroscopic study of a DNA duplex with mercury-mediated T-T base pairs.

Recently, we reported that T-T mismatches can specifically recognize Hg(II) (T-Hg(II)-T pair formation). In order to understand the properties of the T-Hg(II)-T pair, we recorded NMR spectra for a DNA duplex, d(CGCGTTGTCC).d(GGACTTCGCG), with two successive T-T mismatches (Hg (II)-binding sites). We assigned 1H resonances for mercury-free and di-mercurated duplexes, and performed titration experiments with Hg(II) by using 1D 1H NMR spectra. Because of the above mentioned assignments, we could confirm the existence of mono-mercurated species, because individual components gave independent NMR signals in the titration spectra.

MercuryII-mediated formation of thymine-HgII-thymine base pairs in DNA duplexes.

The very specific binding of the HgII ion unexpectedly and significantly stabilizes naturally occurring thymine-thymine base mispairing in DNA duplexes. Following this finding, we prepared DNA duplexes containing metal-mediated base pairs at the desired sites, as well as novel double helical architectures consisting only of thymine-HgII-thymine pairs.

NMR spectroscopic analyses of functional nucleic acids-metal interaction and their solution structure analyses.

We have studied complexations of functional nucleic acids and metal ions, by means of NMR spectroscopy. In the case of hammerhead ribozymes, they have a metal ion-binding motif in their core sequences. Upon the metallation of N7 of a guanosine in an RNA duplex modelled after hammerhead ribozymes, 20 ppm higher field shift of N7 was observed in 1-dimensional (1D) 15N NMR spectra. It was found that metal ion binding to nucleobases were detectable with 15N NMR spectroscopy.

Spectroscopic analyses of DNA duplexes in the presence of mercury ions.

The DNA duplex with tandem T x T mismatches in the presence of Hg(II) has been studied by NMR spectroscopy. For this study, we synthesized decamer duplex with two successive T x T mismatches (TT10). From two-dimensional (2D) 1H-1H NOESY spectrum of TT10 in complex with Hg(II), we were able to trace sequential NOE walks between base protons and anomeric protons (H1'), and assigned all of them. Based on these assignments and NOESY spectra, we could assigned all the non-exchangeable protons of TT10 in the presence of Hg(II).

Spectroscopic analysis of DNA duplexes including T-T mismatches.

The DNA duplex with tandem T x T mismatches has been studied by NMR spectroscopy. For this study, we synthesized decamer duplex with two successive T x T mismatches, TT10:d(CGCGTTGTCC) x d(GGACTTCGCG). From two-dimensional (2D) 1H-1H NOESY spectrum, we were able to trace sequential NOE walks between base protons and anomeric protons (H1'), and assigned all the base protons and anomeric protons. These results indicate that the overall structure of the duplex is a right-handed duplex, with two successive T x T mismatches stacked in the helix.