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1.  Adjunctive GnRH-a treatment attenuates depletion of ovarian reserve associated with cyclophosphamide therapy in pre-menopausal SLE patients 
Gynecological Endocrinology  2012;28(8):624-627.
We measured anti-Mullerian hormone (AMH), a marker of ovarian reserve, in women with lupus treated with cyclophosphamide (CYC) (Group I), CYC plus gonadotropin-releasing hormone agonist (GnRH-a) (Group II), or neither (Group III). We hypothesized that AMH would be diminished in women exposed to CYC vs women receiving adjunctive GnRH-a treatment or no CYC exposure.
48 pre-menopausal lupus patients were retrospectively divided into three treatment groups: CYC alone (Group I, n=11), CYC + GnRH-a (Group II, n=10), neither (Group III, n=27). Serum AMH levels between groups were compared using a non-parametric test (Wilcoxon rank-sum). Multiple linear regression adjusting for age was performed.
AMH (ng/mL) levels at the last collection were significantly lower in Group I vs Group III (mean ± SD: 0.18 ± 0.20 Group I vs 1.33 ± 1.59 Group III; p=0.015), and vs Group II (mean ± SD: 0.86 ± 1.06; p=0.018). When centered on age 30 years, average AMH levels for Group I, Group II, and Group III were: 0.20, 0.44, and 1.00, respectively. When adjusted for age, AMH between all groups was significantly different (p<0.0001).
Post-treatment AMH levels were significantly higher among patients receiving CYC + GnRH-a compared to CYC alone, suggesting that GnRH-a co-administration mitigates CYC-induced ovarian injury.
PMCID: PMC3396751  PMID: 22296584
anti-Mullerian hormone (AMH); primary ovarian insufficiency; cyclophosphamide; systemic lupus erythematosus
2.  Adrenal Androgens and the Menopausal Transition 
The concept that adrenal androgen production gradually declines with age has changed following the analysis of the longitudinal data collected in the Study of Women’s Health Across the Nation (SWAN). It is now recognized that four adrenal androgens (3-beta hydroxy-5-androsten-17-one or dehydroepiandrosterone--DHEA, its sulfate, dehydroepiandrosterone sulfate--DHEAS; androst-4-ene, 3,17-dione or androstenedione; and androst-5-ene-3-beta, 17-beta diol, also known as androstenediol or Adiol) rise during the menopausal transition in most women. Ethnic and individual differences in sex steroids are more apparent in circulating adrenal steroids than in either estradiol or cyclic ovarian steroid hormone profiles, particularly during the early and late perimenopause. Thus, adrenal steroid production may play a larger role in the occurrence of symptoms and the potential for healthier aging than previously recognized.
PMCID: PMC3185242  PMID: 21961714
menopausal transition; androgens; adrenal
4.  Predictors of recovery of ovarian function during aromatase inhibitor therapy 
Annals of Oncology  2013;24(8):2011-2016.
Aromatase inhibitors (AIs) may cause a rise in estrogen levels due to ovarian function recovery in women with clinical chemotherapy-induced ovarian failure (CIOF). We carried out a prospective registry trial to identify predictors of ovarian function recovery during AI therapy.
Patients and methods
Women with hormone receptor (HR)-positive breast cancer who remained amenorrheic and had hormonal levels consistent with ovarian failure after adjuvant chemotherapy were enrolled in a multi-institutional clinical trial of anastrozole. Subjects underwent frequent assessment using an ultrasensitive estradiol assay. Multivariable analysis was used to evaluate clinical and biochemical predictors of ovarian function recovery within 48 weeks.
Recovery of ovarian function during AI therapy was observed in 13 of 45 (28.9%) assessable subjects after a median 2.1 months (range 0.6–11.9). Median age at chemotherapy initiation was statistically significantly different between those who regained ovarian function (43 years, range 40–51) and those who remained postmenopausal (49 years, range 44–52; P < 0.0001).
A significant proportion of women with CIOF recover ovarian function during AI therapy, including a woman over age 50 at initiation of chemotherapy. Tamoxifen remains the standard of care for women with CIOF. If an AI is used, patients should be monitored frequently with high-quality estradiol assays. NCT00555477.
PMCID: PMC3718506  PMID: 23613476
aromatase inhibitor; breast cancer; chemotherapy-induced ovarian failure; estradiol; ovarian function
5.  Evaluation of the trade-offs encountered in planning and treating locally advanced head and neck cancer: intensity-modulated radiation therapy vs dual-arc volumetric-modulated arc therapy 
The British Journal of Radiology  2012;85(1020):1539-1545.
The primary purpose of this study was to assess the practical trade-offs between intensity-modulated radiation therapy (IMRT) and dual-arc volumetric-modulated arc therapy (DA-VMAT) for locally advanced head and neck cancer (HNC).
For 15 locally advanced HNC data sets, nine-field step-and-shoot IMRT plans and two full-rotation DA-VMAT treatment plans were created in the Pinnacle3 v. 9.0 (Philips Medical Systems, Fitchburg, WI) treatment planning environment and then delivered on a Clinac iX (Varian Medical Systems, Palo Alto, CA) to a cylindrical detector array. The treatment planning goals were organised into four groups based on their importance: (1) spinal cord, brainstem, optical structures; (2) planning target volumes; (3) parotids, mandible, larynx and brachial plexus; and (4) normal tissues.
Compared with IMRT, DA-VMAT plans were of equal plan quality (p>0.05 for each group), able to be delivered in a shorter time (3.1 min vs 8.3 min, p<0.0001), delivered fewer monitor units (on average 28% fewer, p<0.0001) and produced similar delivery accuracy (p>0.05 at γ2%/2mm and γ3%/3mm). However, the VMAT plans took more planning time (28.9 min vs 7.7 min per cycle, p<0.0001) and required more data for a three-dimensional dose (20 times more, p<0.0001).
Nine-field step-and-shoot IMRT and DA-VMAT are both capable of meeting the majority of planning goals for locally advanced HNC. The main trade-offs between the techniques are shorter treatment time for DA-VMAT but longer planning time and the additional resources required for implementation of a new technology. Based on this study, our clinic has incorporated DA-VMAT for locally advanced HNC.
Advances in knowledge
DA-VMAT is a suitable alternative to IMRT for locally advanced HNC.
PMCID: PMC3611711  PMID: 22806619
6.  Testosterone, sex hormone-binding globulin and free androgen index among adult women: chronological and ovarian aging 
Human Reproduction (Oxford, England)  2009;24(9):2276-2285.
In this study, levels and rates of change in total testosterone (T), sex hormone-binding globulin (SHBG) and free androgen index (FAI) were related to chronological age and to the final menstrual period (FMP) as an indicator of ovarian aging.
Data were annually acquired over a 15-year period in 629 women of the Michigan Bone Health and Metabolism Study cohort. Data were censored for hormone therapy use. Endogenous androgen patterns over time were described with stochastic processes and bootstrapping.
With ovarian aging, T levels rose from a mean of 18 ng/dl commencing 10 years prior to the FMP to 27 ng/dl at the FMP. Over the 20-year period encompassing the FMP, modeled mean SHBG levels changed from 58 to 34 nM and the FAI ratio increased from 1.6 to 2.9 in a non-linear manner. With chronological aging, total T levels increased (P < 0.0001) from 43 to 50 years, but not thereafter. SHBG declined steadily with age with a modestly greater rate of change between 49 and 54 years. The FAI increased from 1.3 to 2.5 from 34 to 58 years.
T increased from approximately age 40 until the FMP whereas SHBG had rate of change patterns reflecting both chronological and ovarian aging components. These data provide new insight into the endogenous androgen patterns at mid-life.
PMCID: PMC2733826  PMID: 19520711
reproductive senescence; hormone trajectories; total testosterone; androgens; ovarian aging
7.  Audiotapes and letters to patients: the practice and views of oncologists, surgeons and general practitioners 
British Journal of Cancer  1999;79(11-12):1782-1788.
A range of measures have been proposed to enhance the provision of information to cancer patients and randomized controlled trials have demonstrated their impact on patient satisfaction and recall. The current study explored the practice and views of oncologists, surgeons and general practitioners (GPs) with regards to providing patients with consultation audiotapes and summary letters. In stage 1, 28 semi-structured interviews with doctors were conducted to provide qualitative data on which to base a questionnaire. In stage 2, 113 medical oncologists, 43 radiation oncologists, 55 surgeons and 108 GPs completed questionnaires. Only one-third of doctors had ever provided patients with a copy of the letter written to the oncologist or referring doctor, and one-quarter had provided a summary letter or tape. The majority of doctors were opposed to such measures; however, a substantial minority were in favour of providing a letter or tape under certain conditions. More surgeons and GPs (> two-thirds) were opposed to specialists providing a consultation audiotape than oncologists (one-third). Gender, years of experience and attitude to patient involvement in decision-making were predictive of doctors' attitudes. The majority of doctors remain opposed to offering patients personalized information aids. However, practice and perspectives appear to be changing. © 1999 Cancer Research Campaign
PMCID: PMC2362803  PMID: 10206293
Dr-pt communication; information provision; audiotapes; patient letters
8.  Overproduction, isolation, and DNA-binding characteristics of Xre, the repressor protein from the Bacillus subtilis defective prophage PBSX. 
Journal of Bacteriology  1994;176(18):5831-5834.
PBSX is a phage-like bacteriocin (phibacin) of Bacillus subtilis 168. Lysogeny is maintained by the PBSX-encoded repressor, Xre. The Xre protein was overproduced in Escherichia coli and isolated by affinity chromatography. Gel retardation and DNase I footprinting studies indicated that Xre binds to four sites close to its own gene. These sites overlap putative promoters for xre and a divergent transcriptional unit, containing the middle genes.
PMCID: PMC196788  PMID: 8083175
9.  Genetic control of bacterial suicide: regulation of the induction of PBSX in Bacillus subtilis. 
Journal of Bacteriology  1994;176(18):5820-5830.
PBSX is a phage-like bacteriocin (phibacin) of Bacillus subtilis 168. Bacteria carrying the PBSX genome are induced by DNA-damaging agents to lyse and produce PBSX particles. The particles cannot propagate the PBSX genome. The particles produced by this suicidal response kill strains nonlysogenic for PBSX. A 5.2-kb region which controls the induction of PBSX has been sequenced. The genes identified include the previously identified repressor gene xre and a positive control factor gene, pcf. Pcf is similar to known sigma factors and acts at the late promoter PL, which has been located distal to pcf. The first two genes expressed from the late promoter show homology to genes encoding the subunits of phage terminases.
PMCID: PMC196787  PMID: 8083174
10.  Expression of a gene family in the dimorphic fungus Mucor racemosus which exhibits striking similarity to human ras genes. 
Molecular and Cellular Biology  1990;10(12):6654-6663.
Sporulation, spore germination, and yeast-hypha dimorphism in the filamentous fungus Mucor racemosus provide useful model systems to study cell development in eucaryotic cells. Three RAS genes (MRAS1, MRAS2, and MRAS3) from M. racemosus have been cloned, and their nucleotide sequences have been determined. The predicted amino acid sequences and the sizes of the three MRAS proteins exhibit a high degree of similarity with other ras proteins, including that encoded by H-ras, which have been implicated in regulation of proliferation and development in eucaryotic cells by mediating signal transduction pathways. The MRAS proteins show conservation of functional domains proposed for ras proteins, including guanine nucleotide interaction domains, an effector domain, a binding epitope for neutralizing antibody Y13-259, and the COOH-terminal CAAX box, which is a site of thiocylation and membrane attachment. Amino acid sequences unique to each MRAS protein occur adjacent to the CAAX box, consistent with the location of the hypervariable region in other ras proteins. Northern (RNA) analysis was used to study expression of the three MRAS genes in relation to cell development. Gene-specific probes for two of these genes, MRAS1 and MRAS3, hybridized to different 1.3-kb mRNA transcripts. The accumulation of these transcripts depended on the developmental stage, and this pattern was different between the two MRAS genes. No transcript for MRAS2 was detected in the developmental stages examined. The unique patterns of MRAS transcript accumulation suggest that individual MRAS genes and proteins may play distinct roles in cell growth or development.
PMCID: PMC362943  PMID: 1701021
11.  Molecular analysis of an IS200 insertion in the gpt gene of Salmonella typhimurium LT2. 
Journal of Bacteriology  1990;172(11):6599-6601.
A strain of Salmonella typimurium LT2 has been isolated which carries an insertion of approximately 700 bp in the gpt gene. The insertion in the gpt gene was shown to be the Salmonella-specific element IS200. The mutation in strain CR1 arose without selection during storage and is only the second phenotypically identified mutation caused by the insertion of IS200.
PMCID: PMC526853  PMID: 2172218
12.  Characterization of PBSX, a defective prophage of Bacillus subtilis. 
Journal of Bacteriology  1990;172(5):2667-2674.
PBSX, a defective Bacillus subtilis prophage, maps to the metA-metC region of the chromosome. DNA (33 kilobases) from this region of the chromosome was cloned and analyzed by insertional mutagenesis with the integrating plasmid pWD3. This plasmid had a promoterless alpha-amylase gene (amyL) that provided information on the direction and level of transcription at the site of integration. Transcription under the control of the PBSX repressor proceeded in the direction metA to metC over a distance of at least 18 kilobases. Electrophoretic analysis of proteins produced by different integrant strains upon PBSX induction and by fragments subcloned in Escherichia coli allowed the identification of early and late regions of the prophage. A set of contiguous fragments directing mutagenic integration suggested that the minimum size of an operon that encodes phage structural proteins is 19 kilobases. The adaptation of PBSX transcriptional and replicational functions to a chromosomally based, thermoinducible expression system is discussed.
PMCID: PMC208911  PMID: 2110147
13.  cis sequences involved in modulating expression of Bacillus licheniformis amyL in Bacillus subtilis: effect of sporulation mutations and catabolite repression resistance mutations on expression. 
Journal of Bacteriology  1989;171(5):2443-2450.
Nutrient conditions which trigger sporulation also activate expression of the Bacillus licheniformis alpha-amylase gene, amyL. Glucose represses both spore formation and expression of amyL. A fusion was constructed between the B. licheniformis alpha-amylase regulatory and 5' upstream sequences (amyRi) and the Escherichia coli lacZ structural gene to identify sequences involved in mediating temporal activation and catabolite repression of the amyL gene in Bacillus subtilis. amyRi-directed expression in a variety of genetic backgrounds and under different growth conditions was investigated. A 108-base-pair sequence containing an inverted repeat sequence, ribosome-binding site, and 26 codons of the structural gene was sufficient to mediate catabolite repression of amyL. spo0 mutations (spo0A, spo0B, spo0E, and spo0H) had no significant effect on temporal activation of the gene fusion when the recipient strains were grown in nonrepressing medium. However, in glucose-grown cultures the presence of a spo0A mutation resulted in more severe repression of amyRi-lacZ. In contrast, a spo0H mutation reduced the repressive effect of glucose on amyRi-lacZ expression. The spo0A effect was relieved by an abrB mutation. Initiation of sporulation is not a prerequisite for either temporal activation or derepression of alpha-amylase synthesis. Mutations causing resistance to catabolite repression in B. subtilis GLU-47, SF33, WLN30, and WLN104 also relieved catabolite repression of amyRi-lacZ.
PMCID: PMC209919  PMID: 2496107
14.  Bacillus licheniformis alpha-amylase gene, amyL, is subject to promoter-independent catabolite repression in Bacillus subtilis. 
Journal of Bacteriology  1989;171(5):2435-2442.
Expression of the Bacillus licheniformis alpha-amylase gene, amyL, was temporally activated and subject to catabolite repression both in its natural host and when cloned on a 3.55-kilobase fragment in Bacillus subtilis. A subclone from which the promoter region of amyL and sequences upstream from the promoter were deleted had a low level of amylase activity. Expression of the promoterless gene was still subject to repression by glucose when the gene was present either on a multicopy plasmid or integrated into the B. subtilis chromosome. Catabolite repression occurred independently of the amylase promoter and irrespective of the distance of the promoterless amyL gene from the promoter which transcribed it. The transcriptional start sites of amyL activated by its own promoter and by a vector sequence promoter were determined by S1 mapping. alpha-Amylase-specific mRNA levels were measured in repressing and nonrepressing media, and catabolite repression was found to act at the level of transcription.
PMCID: PMC209918  PMID: 2540150
15.  Replication and segregational stability of Bacillus plasmid pBAA1. 
Journal of Bacteriology  1989;171(2):1166-1172.
A cryptic plasmid, pBAA1, was identified in an industrial Bacillus strain. The plasmid is 6.8 kilobases in size and is present in cells at a copy number of approximately 5 per chromosome equivalent. The plasmid has been maintained under industrial fermentation conditions without apparent selective pressure and so is assumed to be partition proficient. The minimal replicon was localized to a 1.4-kilobase fragment which also contains the functions required for copy number control. The very low level of segregational instability of the minimal replicon suggests that it also contains functions involved in plasmid maintenance. Comparison with other plasmids indicates that pBAA1 belongs to the group of small gram-positive plasmids which replicate by a rolling cycle-type mechanism. A sequence was identified which is required for the efficient conversion of the single plus strand to the double-stranded form during plasmid replication. Deletion of this sequence resulted in a low level of segregational plasmid instability.
PMCID: PMC209715  PMID: 2492507
16.  Linkage analysis of X linked retinitis pigmentosa in the Irish population. 
Journal of Medical Genetics  1988;25(4):222-226.
There is significant evidence for genetic and phenotypic heterogeneity in X linked retinitis pigmentosa (XLRP). We have studied the linkage of XLRP in four Irish families to a number of polymorphic DNA markers. We report linkage between the DXS7 (L1.28) locus and the XLRP locus (Z = 3.445, theta = 0.00). Combined with the previously published data on British and Danish families, the genetic distance between the DXS7 and XLRP loci is now estimated at 5 cM with a maximum lod score of 13.026 and a 1-lod confidence interval of 0.75 to 9.5 cM. Linkage was also observed between 754 and XLRP (Z = 3.41, theta = 0.00) and between pERT87 and XLRP (Z = 1.37, theta = 0.1). The heterogeneity of XLRP is discussed in relation to these observations.
PMCID: PMC1015500  PMID: 3163380
17.  Relationship among oxidative stress, growth cycle, and sporulation in Bacillus subtilis. 
Journal of Bacteriology  1987;169(12):5771-5775.
The sensitivity of Bacillus subtilis to hydrogen peroxide (oxidative stress) was found to vary with the position of the culture in the growth cycle. The most dramatic change occurred at the stationary phase, when the cells became totally resistant to 10 mM H2O2, in contrast to the loss of 3 to 4 log units of viability when treated at the early log phase. Two of the eight proteins induced by a protective concentration of H2O2 (50 muM) were also induced (in the absence of oxidative stress) on entry into the late log phase of growth. The response of five isogenic spo0 mutants (spo0B, spo0E, spo0F, spo0H, and spo0J) to oxidative stress was identical to that of the wild-type parental strain. In an isogenic spo0A strain, mid-log-phase cells were 100-fold less sensitive to 10 mM H2O2 than was the wild type. Pretreatment with 50 microM H2O2 induced little further protection, suggesting that the response is constitutive in this strain. By comparison of proteins induced by 50 microM H2O2 in the wild-type, spo0A, spo0H, and spo0J strains, four proteins were identified that may be essential for protection against lethal concentrations of H2O2. The presence of multiple copies of the spo0H gene in a spo0A background converted the stress phenotype of the spo0A mutant to that of the wild type but left the sporulation phenotype unaltered.
PMCID: PMC214128  PMID: 3119569
18.  Oxidative stress and growth temperature in Bacillus subtilis. 
Journal of Bacteriology  1987;169(12):5766-5770.
Pretreatment of Bacillus subtilis with low concentrations of hydrogen peroxide protected the cells against the lethal effects of higher levels of oxidative stress. During the period of adaptation, eight proteins were induced, as detected by one-dimensional gel electrophoresis. Four of these proteins were the same size as four of the proteins induced by the temperature upshift. The range of proteins synthesized in response to an elevation in temperature depended both on the starting (lower) temperature and on the temperature to which the cells were shifted. Both catalase and superoxide dismutase were present at high levels in B. subtilis, but neither was induced by oxidative stress or temperature upshift. In fact, catalase activity was reduced after the temperature upshift.
PMCID: PMC214122  PMID: 3119568
19.  Expression of the gene for NAD-dependent glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides cloned in Escherichia coli K-12. 
Journal of Bacteriology  1987;169(1):334-339.
The structural gene (zwf) for Leuconostoc mesenteroides glucose-6-phosphate dehydrogenase has been cloned into Escherichia coli on pBR322 by selecting for complementation of a zwf mutation of E. coli which eliminates glucose-6-phosphate dehydrogenase. The gene has been subcloned on a 3.4-kilobase DNA segment. The encoded glucose-6-phosphate dehydrogenase displays the dual nucleotide specificity (reacting with NAD and NADP) of the L. mesenteroides enzyme and has a subunit Mr of 55,000. A second gene encoding protein of subunit Mr 24,000 is also encoded on the 3.4-kilobase DNA segment. The genes have been located by the analysis of deletions and insertions generated in vitro and by transcriptional mapping with a promoterless chloramphenicol acetyl transferase cartridge inserted at different sites in the 3.4-kilobase fragment.
PMCID: PMC211772  PMID: 3025177
20.  Integrable alpha-amylase plasmid for generating random transcriptional fusions in Bacillus subtilis. 
Journal of Bacteriology  1986;168(2):973-981.
An integrable plasmid, pOK4, which replicated independently in Escherichia coli was constructed for generating transcriptional fusions in vivo in Bacillus DNA. It did not replicate independently in Bacillus subtilis, but it could be made to integrate into the chromosome of B. subtilis if sequences homologous to chromosomal sequences were inserted into it. It had a selectable marker for chloramphenicol resistance and carried unique sites for EcoRI and SmaI just to the 5' side of a promoterless alpha-amylase gene from Bacillus licheniformis. When B. subtilis DNA fragments were ligated into one of these sites and the ligation mixture was used to transform an alpha-amylase-negative B. subtilis strain, chloramphenicol-resistant transformants could be isolated conveniently. Many of these were alpha-amylase positive, owing to the fusion of the plasmid amylase gene to chromosomal operons. In principle, because integration need not be mutagenic, it is possible to obtain fusions to any chromosomal operon. The site of each integration can be mapped, and the flanking sequences can be cloned into E. coli. The alpha-amylase gene can be used to detect regulated genes. We used it as an indicator to detect operons which are DNA-damage-inducible (din), and we identified insertions in both SP beta and PBSX prophages.
PMCID: PMC213579  PMID: 3096966
22.  Nucleotide sequence of the 5' region of the Bacillus licheniformis alpha-amylase gene: comparison with the B. amyloliquefaciens gene. 
Journal of Bacteriology  1984;158(1):369-372.
The DNA sequence of the 5' region of the Bacillus licheniformis alpha-amylase gene is reported. Comparison of the inferred amino acid sequence of the B. licheniformis alpha-amylase gene with that of the Bacillus amyloliquefaciens gene shows that whereas the amino acid sequences of the mature proteins have considerable homology, the sequences for the signal peptides are distinct.
PMCID: PMC215428  PMID: 6609154
23.  Physical map of Salmonella typhimurium LT2 DNA in the vicinity of the proA gene. 
Journal of Bacteriology  1984;157(2):655-657.
More than 55 kilobases of chromosomal DNA of Salmonella typhimurium LT2, including the gpt, proA, ataA, and newD genes, were cloned in plasmid vector pULB113. The locations of the genes and selected restriction endonuclease cleavage sites were established, and some of the restriction enzyme fragments were subcloned in plasmid vector pBR322.
PMCID: PMC215297  PMID: 6319371
24.  A comparative study of the interaction of 5,10,15,20-tetrakis (N-methylpyridinium-4-yl)porphyrin and its zinc complex with DNA using fluorescence spectroscopy and topoisomerisation. 
Nucleic Acids Research  1985;13(1):167-184.
Binding of 5,10,15,20-tetrakis (N-methylpyridinium-4-yl)porphyrin (H2TMPyP4+) and its zinc complex (ZnTMPyP4+) to DNA is demonstrated by their coelectrophoresis and by absorption and fluorescence spectroscopic methods. Topoisomerisation of pBR322 DNA shows that H2TMPyP4+ unwinds DNA as efficiently as ethidium bromide showing that it intercalates at many sites. ZnTMPyP4+ may cause limited unwinding. Marked changes in the fluorescence spectra of the porphyrins are found in the presence of DNA. The fluorescence intensity of either H2TMPyP4+ or ZnTMPyP4+ is enhanced in the presence of poly (d(A-T)), whereas in the presence of poly (d(G-C] the fluorescence intensity of ZnTMPyP4+ is only slightly affected and that of H2TMPyP4+ markedly reduced. Both the porphyrins photosensitize the cleavage of DNA in aerated solution upon visible light irradiation.
PMCID: PMC340982  PMID: 2987789
25.  Methylene blue photosensitised strand cleavage of DNA: effects of dye binding and oxygen. 
Nucleic Acids Research  1987;15(18):7411-7427.
It is shown that methylene blue (MB+) photosensitises DNA in either aerated or deaerated solutions, causing direct cleavage of phosphodiester bonds and rendering additional bonds labile to alkali. Evidence from unwinding and fluorimetric studies indicates that MB+ binds to DNA in at least 2 ways. Intercalation, which optimally induces helical unwinding of 24 degrees +/- 2 degrees per MB+, is markedly reduced upon neutralisation by Mg2+ of the DNA phosphates, while significant non-intercalative binding persists as shown by substantial fluorescence quenching at Mg2+ concentrations where there is little unwinding. MB+ induces photolysis at both low and high Mg2+ concentration - intercalation is apparently not required for photolysis. The quantum yield for strand breakage varies from 1-3 X 10(-7) under different conditions and is oxygen enhanced. The DNA cleavage is guanine specific. The 3' termini of the primary MB+-induced DNA photoproducts, unlike those generated by chemical sequencing retain an alkali labile adduct on the terminal phosphate.
PMCID: PMC306257  PMID: 2821508

Results 1-25 (30)