Please wait, while we are loading the content...
Please wait, while we are loading the content...
| Content Provider | PubMed Central |
|---|---|
| Author | Fisher, J. R. E. Rosenbach-belkin, V. Scherz, A. |
| Abstract | The aggregation of bacteriochlorophyll a and bacteriopheophytin a into large oligomers with maximum optical absorption at 860 nm was studied in a 3:1 (vol/vol) formamide/water solution, using optical absorption spectroscopy and electron microscopy. The aggregation is cooperative and proceeds according to two equilibrium constants. Initially, two pigment molecules form a “seed” that absorbs at ≈860 nm. The equilibrium constant, K a, governing this reaction equals 1.3 × 103 M-1 in the case of bacteriochlorophyll a (due to experimental limitations, K a for bacteriopheophytin a could not be determined). The addition of monomers to aggregates consisting of two or more units is governed by an equilibrium constant, K b, equal to 2.2 × 106 M-1 for bacteriochlorophyll a and ≈ 109 M-1 for bacteriopheophytin a. The enthalpy and entropy changes that drive the bacteriochlorophyll oligomer formation are -9.25 and ≈0.0 kcal/mol, respectively. Above a threshold concentration, the amount of oligomers remains constant but their length continues to increase. Each oligomer appears to consist of dimers that are associated by hydrophobic interactions among their alcohol residues, forming long strands. Single strands presumably coil into helices that are seen as cylinders. The bacteriochlorophyll a oligomers form cylinders with a constant diameter of 150 Å and an average length of 2,000 Å (at 1.5 × 10-5 M bacteriochlorophyll a). These cylinders contain 200-250 bacteriochlorophyll a dimers. The bacteriopheophytin oligomers coil into wider cylinders (≈400 Å in diameter) which contain ≈600-700 bacteriopheophytin a dimers. In both cases, the separation between the dimers is ≈20 Å. At such distances, the dipolar interactions among adjacent dimers are negligible and do not affect the optical absorption of each individual pair. Therefore, the optical absorption of these pairs can be a tool for investigating the absorption pattern of photosynthetic pigments in vivo. |
| Starting Page | 461 |
| File Format | |
| ISSN | 15420086 |
| e-ISSN | 15420086 |
| Journal | Biophysical Journal |
| Issue Number | 2 |
| Volume Number | 58 |
| Language | English |
| Publisher Date | 1990-08-01 |
| Access Restriction | Open |
| Subject Keyword | Research in Higher Education |
| Content Type | Text |
| Resource Type | Article |
| Subject | Biophysics |
National Digital Library of India (NDLI) is a virtual repository of learning resources which is not just a repository with search/browse facilities but provides a host of services for the learner community. It is sponsored and mentored by Ministry of Education, Government of India, through its National Mission on Education through Information and Communication Technology (NMEICT). Filtered and federated searching is employed to facilitate focused searching so that learners can find the right resource with least effort and in minimum time. NDLI provides user group-specific services such as Examination Preparatory for School and College students and job aspirants. Services for Researchers and general learners are also provided. NDLI is designed to hold content of any language and provides interface support for 10 most widely used Indian languages. It is built to provide support for all academic levels including researchers and life-long learners, all disciplines, all popular forms of access devices and differently-abled learners. It is designed to enable people to learn and prepare from best practices from all over the world and to facilitate researchers to perform inter-linked exploration from multiple sources. It is developed, operated and maintained from Indian Institute of Technology Kharagpur.
Learn more about this project from here.
NDLI is a conglomeration of freely available or institutionally contributed or donated or publisher managed contents. Almost all these contents are hosted and accessed from respective sources. The responsibility for authenticity, relevance, completeness, accuracy, reliability and suitability of these contents rests with the respective organization and NDLI has no responsibility or liability for these. Every effort is made to keep the NDLI portal up and running smoothly unless there are some unavoidable technical issues.
Ministry of Education, through its National Mission on Education through Information and Communication Technology (NMEICT), has sponsored and funded the National Digital Library of India (NDLI) project.
| Sl. | Authority | Responsibilities | Communication Details |
|---|---|---|---|
| 1 | Ministry of Education (GoI), Department of Higher Education |
Sanctioning Authority | https://www.education.gov.in/ict-initiatives |
| 2 | Indian Institute of Technology Kharagpur | Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project | https://www.iitkgp.ac.in |
| 3 | National Digital Library of India Office, Indian Institute of Technology Kharagpur | The administrative and infrastructural headquarters of the project | Dr. B. Sutradhar bsutra@ndl.gov.in |
| 4 | Project PI / Joint PI | Principal Investigator and Joint Principal Investigators of the project |
Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon |
| 5 | Website/Portal (Helpdesk) | Queries regarding NDLI and its services | support@ndl.gov.in |
| 6 | Contents and Copyright Issues | Queries related to content curation and copyright issues | content@ndl.gov.in |
| 7 | National Digital Library of India Club (NDLI Club) | Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach | clubsupport@ndl.gov.in |
| 8 | Digital Preservation Centre (DPC) | Assistance with digitizing and archiving copyright-free printed books | dpc@ndl.gov.in |
| 9 | IDR Setup or Support | Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops | idr@ndl.gov.in |
|
Loading...
|