Photoluminescence and magnetism integrated multifunctional black phosphorus probes through controllable PO bond orbital hybridization.

Biological probes with integrated photoluminescence and magnetism characteristics play a critical role in modern clinical diagnosis and surgical protocols combining fluorescence optical imaging (FOI) with magnetic resonance imaging (MRI) technology. However, traditional magnetic semiconductors can easily generate a spin splitting at the Fermi level and half-metallic electronic occupation, which will sharply reduce the radiation recombination efficiency of photogenerated carriers. To overcome this intrinsic contradiction, we propose a controllable oxidation strategy to introduce some particular PO bonds into black phosphorus nanosheets, in which the p orbital hybridization between P and O atoms not only provides some carrier recombination centers but also leads to a room-temperature spin polarization. As a result, the coexistence of photoluminescence and magnetism is realized in multifunctional black phosphorus probes with excellent biocompatibility. This work provides a new insight into integrating photoluminescence and magnetism together by intriguing atomic orbital hybridization.

Insulin biosynthesis in HIT cells. Effects of glucose, forskolin, IBMX, and dexamethasone.

Glucose, forskolin, 3-isobutyl-1-methylxanthine (IBMX), and dexamethasone were tested as regulators of proinsulin biosynthesis in HIT T-15 cells, which are glucose-responsive simian virus 40-transformed hamster beta-cells. Rate of [3H]leucine incorporation into proinsulin was increased as glucose concentrations were raised from 0 to 20 mM. Biosynthetic rate increases were significant after 48 but not at 4 or 24 h of glucose and were greater for proinsulin than for total extractable proteins. After 48 h, glucose-stimulated proinsulin biosynthesis was unaffected by 10(-6) M forskolin and/or 3 x 10(-5) M IBMX but was specifically and significantly inhibited by 10(-6) M dexamethasone. Four hours of exposure to dexamethasone had no effect. When cells were incubated for 24 h and then continuously labeled for an additional 24 h, cellular conversion of labeled proinsulin to insulin was increased by glucose, and this increase was reversed or inhibited by 10(-6) M dexamethasone. Therefore, proinsulin biosynthesis in transformed HIT T-15 cells is regulated in several ways by metabolites and hormones in a manner that compares with biosynthetic regulation in normal beta-cells.

The 5'-flanking cis-acting elements of the human epsilon-globin gene associates with the nuclear matrix and binds to the nuclear matrix proteins.

The nuclear matrix attachment regions(MARs) and the binding nuclear matrix proteins in the 5'-flanking cis-acting elements of the human epsilon-globin gene have been examined. Using in vitro DNA-matrix binding assay, it has been shown that the positive stage-specific regulatory element (epsilon-PREII, -446 bp(-)-419 bp) upstream of this gene could specifically associate with the nuclear matrix from K562 cells, indicating that epsilon-PREII may be an erythroid-specific facultative MAR. In gel mobility shift assay and Southwestern blotting assay, an erythroid-specific nuclear matrix protein (epsilon-NMP kappa) in K562 cells has been revealed to bind to this positive regulatory element (epsilon-PREII). Furthermore, we demonstrated that the silencer (-392 bp(-)-177 bp) upstream of the human epsilon-globin gene could associate with the nuclear matrices from K562, HEL and Raji cells. In addition, the nuclear matrix proteins prepared from these three cell lines could also bind to this silencer, suggesting that this silencer element might be a constitutive nuclear matrix attachment region (constitutive MAR). Our results demonstrated that the nuclear matrix and nuclear matrix proteins might play an important role in the regulation of the human epsilon-globin gene expression.

Trans-acting factors from the human fetal liver binding to the human epsilon-globin gene silencer.

The developmental stage-specific silencing of the human epsilon-globin gene during embryonic life is controlled, in part, by the silencer (-392 bp approximately -177 bp) upstream of this gene. In order to elucidate its role, the nuclear extract from the human fetal liver has been prepared and the interactions between trans-acting factors and this silencer element have been examined. By using DNaseI footprinting assay, a major protected region from -278 bp to -235 bp within this silencer element was identified. Furthermore, we found in gel mobility shift assay and Southwestern blotting assay that there were at least four trans-acting factors (MW approximately 32, 28, 26 and 22 kD) in the nuclear extract isolated from the human fetal liver, which could specifically bind to this region. Our results suggested that these trans-acting factors might play an important role in silencing the human embryonic epsilon-globin gene expression at the fetal stage through the interactions with this silencer.

The apoptosis of HEL cells induced by hydroxyurea.

Hydroxyurea has been used to synchronize cultured cells to S-phase and used to treat patients with sickle-cell anemia. Recently, we found that hydroxyurea can induce the apoptosis of HEL (human erythroleukemia) cells. The induced HEL cells showed ultrastructurally chromatin condensation with regular crescents at the nuclear edges and apoptotic bodies. However, the cells of K562, another human erythroleukemia cell line, did not show such morphological changes. Under fluoroscope, the HEL cells after induction often displayed a clear reduction in nuclear diameter and nuclear chromatin cleavage and condensation and the presence of nuclear ring and apoptotic bodies. Analysis with flow cytometry showed that the percentage of apoptotic cells is about 30-40% after HEL cells were induced by hydroxyurea for 3 days. DNA ladder can be observed by electrophoretic analysis.

Function of GATA transcription factors in hydroxyurea-induced HEL cells.

HEL cells, a human erythroleukemia cell line, mainly express the fetal (gamma) globin gene and trace amount of the embryonic (epsilon) globin gene, but not adult (beta) globin gene. Here we show that hydroxyurea (HU) can induce HEL cells to express adult (beta) globin gene and lead these cells to terminal differentiation. Results showed in Gel mobility shift assays that GATA factors could specifically bind to the regulatory elements of human beta-globin gene, including the proximal regulatory element (the beta-promoter) and the distal regulatory elements (the DNase I hypersensitive sites in the LCR, HS2-HS4 core sequences). However, the DNA binding patterns of GATA factors were quite different between HU-induced and uninduced HEL cells. Western-blot analysis of nuclear extracts from both the uninduced and HU-induced HEL cells revealed that the level of GATA-2 transcription factor decreased, whereas the level of GATA-1 transcription factor increased following the time of hydroxyurea induction. Furthermore, using RT-PCR analysis the expression of human beta-globin gene in HU-induced HEL cells could be blocked again when HEL cells were incubated in the presence of antisense oligonucleotides for hGATA-1, suggesting that the upregulation of hGATA-1 transcription factor might be critical for the expression of human beta-globin gene in HU-induced HEL cells.

The structure of the nucleosome core particle of chromatin in chicken erythrocytes visualized by using atomic force microscopy.

The structure of the nucleosome core particle of chromatin in chicken erythrocytes has been examined by using AFM. The 146 bp of DNA wrapped twice around the core histone octamer are clearly visualized. Both the ends of entry/exit of linker DNA are also demonstrated. The dimension of the nucleosome core particles is approximately 1-4 nm in height and approximately 13-22 nm in width. In addition, superbeads (width of approximately 48-57 nm, height of approximately 2-3 nm) are occasionally revealed, two turns of DNA around the core particles are also detected.

Visualization of chromatin folding patterns in chicken erythrocytes by atomic force microscopy (AFM).

The organization of the higher order structure of chromatin in chicken erythrocytes has been examined with tapping-mode scanning force microscopy under conditions close to their native environment. Reproducible high-resolution AFM images of chromatin compaction at several levels can be demonstrated. An extended beads-on-astring (width of approximately 15-20 nm, height of approximately 2-3 nm for each individual nucleosome) can be consistently observed. Furthermore, superbeads (width of approximately 40 nm, height of approximately 7 nm) are demonstrated. Visualization of the solenoid conformation at the level of 30 nm chromatin fiber is attained either by using AFM or by using electron microscopy. In addition, tightly coiled chromatin fibers (approximately 50-60 nm and approximately 90-110 nm) can be revealed. Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning the folding pattern of interphase chromatin fibers.

Characterization of antigen-antibody complexes by size-exclusion chromatography coupled with low-angle light-scattering photometry and viscometry.

In this paper, the molecular masses (M(r)s) of the complexes of monoclonal anti-BSA (antibody to bovine serum albumin) (clone: 33) and monomer BSA were determined on-line by using size-exclusion chromatography (SEC) coupled with a low-angle laser light-scattering (LALLS) detector and two concentration detectors, ultraviolet (UV) and refractive index (RI) (SEC-LALLS/UV/RI system). Also, the size and M(r)s of the complexes were evaluated by the SEC-LALLS/UV/viscometer (VISC) system. This study demonstrated that, for small size macromolecules, the combination of light scattering and viscosity detection was a suitable choice for determining their M(r)s and sizes.

Causes of death and long-term prognosis after myocardial infarction in patients with diabetes mellitus.

The long-term prognosis and causes of death of myocardial infarction (MI) in 62 diabetics were studied. The mean follow-up time was 6.2 years, 11 patients died in the acute stage of MI, 9 of them (81.8%) had anterior infarction and their major causes of death were ventricular fibrillation and cardiogenic shock (72.2%). 19 died in the follow-up period, 14 of them (73.68%) had inferior and anterior septal infarction; and most died of reinfarction and sudden death. The cumulative survival rate 1, 2 and 5 years after MI was 80.7%, 71.9% and 57.9%, respectively. The results suggest that treatment and prevention of MI in patients with diabetes be more attentive to prevent ventricular fibrillation and cardiogenic shock during the acute stage and in the later stage more attention should be paid to preventing reinfarction. At any stage of the disease, strict diabetic control is of vital importance.

[Causes of death and prognosis of myocardial infarction in patients with diabetes].

The long-term prognosis and causes of death of myocardial infarction (MI) in 62 patients with diabetes were studied. The mean follow-up time was 6.2 years. 11 cases died in the acute period of MI (8 weeks following onset of AMI), 9 cases of them (81.8%) had anterior infarction and their major causes of death were ventricular fibrillation and cardiogenic shock (72.2%). 19 cases died in the follow-up period, among them 14 cases (73.68%) had inferior and anterior-septal infarction; most of them died of reinfarction and sudden death. The cumulative survival rate 1.2 and 5 years after MI was 80.7%, 71.9% and 57.9%, respectively. The blood glucose level of the fatal group and the level of CPK and GOT of patients who died in the acute period were higher than those in the surviving group. The results suggest that treatment of myocardial infarction in patients with diabetes be more attentive to prevent ventricular fibrillation and cardiogenic shock during the acute period. After the acute period more attention should be paid to prevent reinfarction and and drop the blood glucose level at normal as possible.

Binding of HMG proteins to the 5'-flanking sequence of human beta-globin gene.

Our previous studies have identified that there are at least three regulatory regions (two negative regions and one positive region) in the 5'-flanking sequence of human beta-globin gene (-610 to +1 bp). The binding of HMG proteins to both negative regulatory regions was examined by the gel mobility shift and DNase I protection assays. In gel mobility shift assay, we observed that HMG proteins 1 and 2 could bind to both negative regulatory regions (NCR1 and NCR2). Using the gel shift competition assay, we identified that the binding proteins between the two regions are different from each other. DNase I protection analysis shows that HMG proteins 1 and 2 only bind to one site (between -560 and -533 bp) in NCR1. However, two protected regions can be detected in NCR2, one between -272 and -252 bp relative to the cap site, the other between -306 and -329 bp. We also observed that HMG proteins 14 and 17 could not bind to both negative regions, so it seems that HMG proteins 1 and 2 may play an important role in the regulation of beta-globin expression through DNA-protein interaction or through protein-protein interaction.

Interaction between HMG proteins (1 + 2) and the negative regulatory region 1 (NCR1) in the 5'-flanking sequence of the human beta-globin gene.

The pattern of high mobility group proteins 1 and 2 (HMG1,2) interaction with the 5'-flanking sequence of the human beta-globin gene has been analyzed by scanning tunnelling microscopy (STM). A 200 bp negative regulatory region in the 5'-flanking sequence of the human beta-globin gene can be folded by HMG proteins 1 and 2 into a circular structure (diameter 70 +/- 6 A) with a linear tail which seems to be a left-handed double helix structure.