400 nm

425 nm

450 nm

475 nm

500 nm

525 nm

550 nm

575 nm

600 nm

625 nm

650 nm

Laser Lines

ArI 488 nm

ArI 514 nm

DPSSL (µGreen) 532 nm

GHeNe 543 nm

YHeNe 594 nm

Red diode 635 nm

Broad UV Excitation290-365 nm

Emission FiltersLP = Long pass filterDF = Band pass filterSP = Short pass filter

555 nm555LP

VersaDoc FiltersMolecular Imager FX Filters

520 nm520LP

660 nm

515 nm

530DF30

545 nm

622.5 nm

640DF35

657.5 nm

580 nm

605DF50

630 nm

670 nm

690DF50

500 nm

530DF60

560 nm

610 nm610LP

660 nm

Excitation Maxima

Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ DAPI: 359 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ GFP (Green Fluorescent Protein): 395 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Coumarin: 402 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ AttoPhos: 440 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Acridine Orange: 460/500 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ R-phycoerythrin: 480/565 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ SYPRO Orange/SYPRO Ruby: 480 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ NanoOrange: 485 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Cy2: 489 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ GelStar: 490 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Oregon Green: 490 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ FAM (5-FAM): 492 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ SYBR Green II: 492 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ FITC: 494 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ SYBR Green I: 494 nm ____Med. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Alexa Fluor 488: 495 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Radiant® Red: 495 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ SYBR Gold: 495 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ SYBR DX: 496 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ OliGreen: 498 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ RiboGreen: 500 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ PicoGreen: 502 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Rhodamine Green: 502 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ BODIPY FL: 503 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Rhodamine 123: 505 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ethidium bromide: 518 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ JOE (6-JOE): 520 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ TET: 520 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Rhodamine R6G: 525 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ BODIPY R6G: 528 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ HEX: 530 nm ____Med. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Alexa Fluor 532: 531 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ BODIPY 530/550: 535 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ethidium bromide homodimer: 535 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Nile Red: 535 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Propidium iodide: 535 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ BODIPY TMR: 542 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ TAMRA (5-TAMRA): 542 nm ____Excel. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ SYPRO Red: 544 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Cy3: 550 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ TM Rhodamine: 554 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Rhodamine Red: 560 nm ____Med. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Alexa Fluor 546: 561 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ROX (5-ROX): 567 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Lissamine Rhodamine: 570 nm ____Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ XRITC: 572 nm ____

Med. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Alexa Fluor 568: 579 nm ____

Med. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Cy3.5: 581 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ BODIPY TR: 589 nm ____Med. ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Alexa Fluor 594: 590 nm ____

Good ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Texas Red: 596 nm ____

Poor ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Alexa Fluor 633: 631 nm ____

Poor ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Cy5: 650 nm ____

Poor ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Cy5.5: 675 nm ____

Emission Maxima

____ 443 nm: Coumarin

____ 461 nm: DAPI

____ 506 nm: Cy2____ 512 nm: BODIPY FL____ 514 nm: Oregon Green____ 517 nm: FAM (5-FAM)____ 518 nm: FITC____ 518 nm: OliGreen____ 519 nm: Alexa Fluor 488____ 520 nm: GelStar____ 520 nm: RiboGreen____ 521 nm: SYBR Green I/SYBR Green II____ 523 nm: PicoGreen____ 526/650 nm: Acridine Orange____ 527 nm: Rhodamine Green

____ 533 nm: Rhodamine 123

____ 537 nm: SYBR Gold____ 540 nm: GFP (Green Fluorescent Protein)____ 540 nm: TET

____ 548 nm: JOE (6-JOE)____ 550 nm: BODIPY R6G____ 550 nm: SYBR DX____ 554 nm: Alexa Fluor 532____ 555 nm: AttoPhos____ 555 nm: BODIPY 530/550____ 555 nm: Rhodamine R6G____ 556 nm: HEX

____ 565 nm: Cy3____ 568 nm: SYPRO Orange____ 568 nm: TAMRA (5-TAMRA)

____ 572 nm: Alexa Fluor 546____ 573 nm: TM Rhodamine____ 574 nm: BODIPY TMR____ 575 nm: Nile Red

____ 578 nm: R-phycoerythrin

____ 580 nm: Rhodamine Red

____ 590 nm: Lissamine Rhodamine____ 590 nm: NanoOrange____ 591 nm: ROX (5-ROX)

____ 595 nm: XRITC____ 596 nm: Cy3.5

____ 603 nm: Alexa Fluor 568____ 605 nm: Ethidium bromide

____ 615 nm: Texas Red____ 617 nm: BODIPY TR____ 617 nm: Ethidium bromide homodimer____ 617 nm: Propidium iodide____ 618 nm: Alexa Fluor 594____ 618 nm: SYPRO Ruby____ 619 nm: SYPRO Red

____ 630 nm: Radiant Red

____ 647 nm: Alexa Fluor 633

____ 670 nm: Cy5

____ 694 nm: Cy5.5

FluorophoreReference GuideFluorophore Excitation and Emission Data

526SP526 nm

I I I I I I I I

Wavelength (nm) 350 400 450 500 550 600 650 700

For more information on Bio-Rad imaging products,contact your local Bio-Rad representative. In the US,call 1-800-4BIORAD (1-800-424-6723).Visit us on the Web at discover.bio-rad.com

Bio-Rad Laboratories, Inc.Life Science Group2000 Alfred Nobel DriveHercules, CA 94547 USA

Alexa Fluor, BODIPY, NanoOrange, OliGreen, Oregon Green, PicoGreen, RiboGreen, SYBR, SYPRO, and Texas Red aretrademarks of Molecular Probes, Inc. AttoPhos is a trademark of JBL Scientific. Cy is a trademark of Amersham PharmaciaBiotech. FAM, HEX, ROX, and TAMRA are trademarks of Applera Corp. GelStar is a trademark of FMC Corp. Lissamine isa trademark of Imperial Chemical Industries PLC. Nile Red is a trademark of Sigma-Aldrich Co.

Bulletin 2421 Rev C 02-060 0502

Spectra:

Excitation Peak Emission PeakResponse to Broad UV Excitation

ExcitationMaxima

EmissionMaxima

Molecular Imager® FXEmission Filter

VersaDoc™

Imaging System EmissionFilter

FluorophoreReference GuideFluorophore Applications and Spectra

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

10080604020

Inte

nsi

ty

Key:

Fluorophore Name Supplier Application

Alexa Fluor 488 Molecular Probes General conjugated label

Good 495 nm 520 nm 530DF30 530DF60

Alexa Fluor 532 Molecular Probes General conjugated label

Good 531 nm 554 nm 550LP/605DF50 520LP

Alexa Fluor 633 Molecular Probes General conjugated label

Good 631 nm 647 nm 695DF50 Not supported

AttoPhos Molecular Probes General conjugated label

Good 440 nm 555 nm 530DF30 Custom

Coumarin Molecular Probes General conjugated label

Good 402 nm 443 nm Not supported Custom

Cy2 Amersham/Pharmacia General conjugated label

Good 489 nm 506 nm 530DF30 530DF60

Cy3 Amersham/Pharmacia General conjugated label

Good 550 nm 565 nm 555LP 520LP

Cy3.5 Amersham/Pharmacia General conjugated label

Medium 581 nm 596 nm 555LP 520LP

Cy5 Amersham/Pharmacia General conjugated label

Good 650 nm 670 nm 695DF55 Not Supported

Ethidium bromide Bio-Rad DNA stain

Good 518 nm 605 nm 555LP 520LP

FITC/FAM Molecular Probes General conjugated label

Good 494 nm 518 nm 530DF30 530DF60

eGFP (Green Fluorescent Protein) Clontech Reporter gene assay

Poor 488 nm 509 nm 530DF30 520LP

HEX ABI General conjugated label

Good 530 nm 556 nm 555LP 520LP

JOE (6-JOE) ABI General conjugated label

Good 520 nm 548 nm 530DF30 520LP

Lissamine Rhodamine Molecular Probes General conjugated label

Good 570 nm 590 nm 555LP 520LP

NanoOrange Molecular Probes Proteins in solution

Excellent 485 nm 590 nm 555LP 520LP

Nile Red Sigma Protein gel stain

Excellent 535 nm 575 nm 555LP 520LP

OliGreen Molecular Probes ssDNA and oligos in solution

Excellent 498 nm 518 nm 530DF30 520LP

Oregon Green Molecular Probes General conjugated label

Excellent 490 nm 514 nm 530DF30 520LP

PicoGreen Molecular Probesd sDNA in solution

Excellent 502 nm 523 nm 530DF30 520LP

Propidium iodide Molecular Probes DNA and cell stain

Good 535 nm 617 nm 555LP/640DF35 610LP

Radiant Red Bio-Rad RNA gel stain

Excellent 495 nm 630 nm 555LP/640DF35 610LP

Rhodamine 123 Molecular Probes General conjugated label

Good 505 nm 533 nm 530DF30 520LP

RiboGreen Molecular Probes RNA in solution

Excellent 500 nm 520 nm 530DF30 520LP

ROX (5-ROX) ABI General conjugated label

Good 567 nm 591 nm 555LP 520LP

R-phycoerythrin Molecular Probes General conjugated label

Good 480/565 nm 578 nm 555LP/530DF30 520LP

SYBR Gold Molecular Probes dsDNA and RNA gel stain

Excellent 495 nm 537 nm 530DF30 520LP

SYBR Green I Molecular Probes dsDNA and RNA gel stain

Excellent 494 nm 521 nm 530DF30 520LP

SYBR Green II Molecular Probes ssDNA and RNA gel stain

Excellent 492 nm 521 nm 530DF30 520LP

SYPRO Orange Bio-Rad Protein gel stain

Excellent 480 nm 568 nm 555LP/530DF30 520LP

SYPRO Red Molecular Probes Protein gel stain

Excellent 544 nm 619 nm 555LP/640DF35 520LP

SYPRO Ruby Molecular Probes Protein gel stain

Excellent 300/480 nm 618 nm 555LP 610LP

TAMRA (5-TAMRA) ABI General conjugated label

Good 542 nm 568 nm 555LP 520LP

Texas Red Molecular Probes General conjugated label

Good 596 nm 615 nm 640DF35 610LP

XRITC Molecular Probes General conjugated label

Good 572 nm 595 nm 555LP/640DF35 520LP